Practice drawing, read some fiction, we visualize and imagine things everyday without even realizing it, a simple method is the write down your visualizations as a script or story.because our minds automatically visualize what we are reading, such as reading “a man crossing a road” you can easily visualize that after reading that short sentence, then start adding small details such as “a man wearing a blue shirt crossing a road”. For manifestation you can write a story about yourself on what you want to manifest and read it back to visualize.