There are some example coding tasks for practice given in the exam guide. It is strongly recommended to do all the questions and maybe ask our peers or professor any questions before the exam.
Also, try to read and study the Drawing App code to the point that you understand how everything works. That will put you in a better position to add new features quickly.
I'm just preparing by doing the coding part and closely looking at DrawingApp since it will be based on that in the exam.
Familiarize yourself with the DrawingApp as much as possible!