After reading some articles about it (that you’ll find below in the resources, if you want to know more), I've seen that sometimes the names and number of the steps change. However, here are the common things which I’ve encountered in most of them: in his book "The Art of Thought", Wallas depicted five stages of creativity:

1. The first one, called "preparation", consists of researching and collecting things we like, in order to find ideas and get inspired.
2. The second one, called "incubation", consists of stop thinking about our goal for a while, and doing other things, in order to let our brain elaborate what we've found. It is a time of subconscious reflection.
3. The third one, called "illumination", is what we commonly associate with being creative, that is, when inspiration strikes. It's the classic light bulb that shines over our head when we have an idea. It can occur when we least expect it.
4. The fourth one, called "evaluation", is when we analyze the idea that we've found. We ask ourselves if it's really good to pursue it, and if so, which way is the best to implement it.
5. The last one, called "verification", consists of materially realizing our idea, and seeing if it works, by sharing it.

That's why no one, not me or anyone else, could ever tell you in detail what to do when it comes about expressing yourself creatively. You need to find your way, and take time in order to learn to trust your own process.

Writing songs is a very individual process, so just trust your process and trust your creative thoughts- Zosia

The good news is that you can take some inspiration from other people: watch videos, read articles, search things that you like and that make you feel inspired. That's what I did when I decided to write about this topic.

And here's what I've learnt about creativity, both from research and from personal experience:

• creativity has it's own way to work, it is not something that we can predict with accuracy. One day we could feel so inspired and want to get things done, while the next day feel like there’s nothing in the world that could makes us start (or maybe, we could feel in both ways in the same day, even at short distance).
• there isn't a unique road to take, a single one that is correct. Trying different ways is important if we want to find what works for us. In fact, the creative process is a continuous discovery: it's a matter of trying things and making mistakes, many mistakes, before having a chance to get where we want to
• coherently to the advice above, you need to take inspiration from somewhere. As Mark Twain once said

  There is no such thing as a new idea. It is impossible. We simply take a lot of old ideas and put them into a sort of mental kaleidoscope. We give them a turn and they make new and curious combinations. We keep on turning and making new combinations indefinitely; but they are the same old pieces of colored glass that have been in use through all the ages.

  Creating something out of thin air is actually not as common as you may think. Most of the time, we draw inspiration from existing ideas, and we mix it with our own experiences, in order to create something original and unique. An interesting article about this subject says that you have to drown in the ocean of influence before you can come up to the surface with something new and exciting. What we can do is get inspiration from the artists we admire, without stealing from them, but taking only what we like and creating something different with our own resources.
• last but not least, creativity is not a gift limited to a few people. Yes, of course, there are some people that seems to have a sort of natural inclination towards one or more than one creative fields. However, even those "creative geniuses" can have bad ideas and find themselves stuck, just like us. In fact, we often admire the works of people who made it, and we would like to know the secret behind their success, but who knows really what they did went through to get to where they are. In short, being creative can be a struggle, for anyone. We need to embrace that struggle, and keep trying.

We may want to add other parts, like:

• an intro and an outro, functional respectively for introducing and ending our story;
• a pre-chorus, that it's like a preparation for our message;
• a bridge, which is a variation, to break the repetitive pattern of the song

What’s important is that the song has a structure, no matter how simple it is. Because without it, even if we’re putting our soul in it, the audience won’t feel it. The reason behind that is that our brains are used to giving order to what we are experiencing. According to this article of the Abbey Road Institute’s blog, When receiving a sequence of sounds, the brain tries to impose structure and order and, in effect, creates an entirely new system of meaning, which translates into a pleasant and rewarding experience or an unpleasant one.

In fact, we can decide in a short time if we like or not a song, because of the structures that our brains built over time, making our “music baggage”. It’s the experience that we have that makes us guess how the song we’re listening will continue. And that will have a role in building our (positive or negative) opinion of the song.

But if there is no structure, our audience will probably be confused. They could not know what we’re trying to say, and consequently not even be able to give an opinion. They’ll just move away from it, and forget it in no time.

And even if it this might sound trivial, it’s essential: if we want our audience to remember our song, they need to feel something when they’re listening to it (positive or negative, that’s up to us and, consistently to what we said above, to them). This last statement is also a reminder: it’s not just about us.

I don't really care what you feel when you write the song, if I don't feel anything when I hear the song - Jason Blume

Of course: it’s our song. Our emotions conveyed in a paper. The song is also about us. But there are two more main characters: our audience, in which we need to put ourselves, trying to look the song from other perspectives, and...the song itself. Yes. As weird as it sounds, our work talks.

It's what the writer Umberto Eco called intentio operis in his book "Lector in Fabula": every artwork is like a living creature, that has a life itself once created by its author. That means that once published, the song won't necessarily convey the meaning that it's author wanted. It could do it obviously, but it also could provide new meanings just by itself (and, certainly, by the interpretations of the audience).