Creativity happens in the process of creating. You are not creative first, it is part of the process.
Therefore to be creative you need to create.
Create constantly.
Creating constantly does two things. First, it builds your skill of being creative. Secondly, a certain percentage of what you create will be good.
Everything you create is not going to be a masterpiece, even when you start with what you think is a great idea. The best approach is to create as much as you can, and then judge what is good.