Start small, don't try to make a perfect clone for you first steps in C2, try to move a sprite, to understand the C2 logic, look at the event available, the conditions, the actions. Start with small challenges or you ll be lost.
Put what you want on paper and write the logic before putting it in C2. It takes time, a lot of time at the beginning, but it's necessary.
(Look at the template : verticale space shooter)