Good luck - I have been downloading and getting someone to digitize for me but have bought Editor Plus V6 for Bernina so hope to start soon.

I usually start with a good outline of what I want to digitize and that where you have to have a good imagination...then I put my background color in and start layering in with the shading a details are last. It helps if you can look at a picture of what you want to do to get an idea of what the subject looks like and colors and details. Sometimes I will have a picture on my desk so I can reference some colors and expressions, when you get good enough you won't need as much visual aid you can draw from your experience....it just takes time and patience and lots of practice.

You don't need anything else. Just start with a nice drawing. Have a good look at it: what comes first, what overlaps what, so you have an idea of the order in which to digitise. Think about using different angles for the filling, the light will reflect differently and give an idea of shading - you'll need less colours that way. And start with something easy, there is a learning curve - you'll be easily disappointed if you aim to high on the first one. And don't forget to test stitch what you've done, watch your machine when you stitch it out, see what's wrong and take notes. That way you can rectify mistakes or unsatisfactory bits far more easily. And it's the only way to learn - never trust the stitching simulator of the software, it's a great help before the first test, but it is not conclusive.
And don't forget it's FUN.