You have two goals: 1. actually get started using visualization-imagination in your life, and 2. get good at these skills. Knowing WHEN to explore and practice these skills will get you off to a great start. The WHEN is probably not the when you expect. Give me 2 minutes and you will be ready to go.
This will be part of a large collection of visualizing instructional videos, guides, and checklists but here are the first 4 minutes. You will get a quick feel for why visualize and what are the major visualizing types.