How to be creative?
Short answer
Stop trying to be.
Long answer
Creativity is not a switch you flip. It is what happens when you are so absorbed in a problem that you forget to perform it. The work calls you in, and you follow.
What I have seen, again and again, is that the people doing the most original work are not chasing originality. They are asking small, stubborn questions. They return to the same material, the same concern, the same obsession, until something shifts. Constraints help. A blank canvas with no rules is often the least creative condition.
The other thing is this: you have to make a lot of bad work. Not as a stepping stone to good work, but as the actual practice. The bad work is not the opposite of creativity. It is where creativity lives, most of the time, quietly, without announcing itself.