If you haven’t drawn connectors, this is where you’ll have a problem, it’s often easier to just re-scan the outline with connectors in it. Also, if your lines are broken up, go back to the drawing and make them heavier or play around with the Image Trace settings.
Now, you have a vector image that can be resized without getting pixelated.
Pick colors in Illustrator. The color will change when texture is added so this becomes a trial and error thing. If I have a specific color I want I’ll add that color to the design in Illustrator and then use it as a reference when I’m adding textures in Photoshop.
I realized my design was missing something during this step, so I added the tree. I separated the trunk and branches because I wanted them to be different colors and it makes for an easier image trace.