Is this for something specific?
As Galileo said, "You cannot teach a man anything; you can only help him to find it within himself"
The creative process is an ongoing exercise. Everything you do that is not habit is creative. You could try puzzles for brain exercise, or create scenarios for success by the power of imagination. Einstein said that imagination is more important than knowledge, so feel free to daydream about achieving something great. Following from that use that idea as a creative focus to go and achieve it for real.
Stimuli can come from anywhere, from past or present experiences, from memory or from dreams. Broaden your horizons through travel, cultural experience or a new challenge, hobby or interest.