I am a noob at coding, I think I may be in over my head here....

My character now summons a cannon as a helper

How do I get the cannon to shoot an actual cannon ball?

The only idea I have is to have the cannonball and cannon share the same sprite, i'm not too sure if that's what I have to do, considering the cannonball should fly across the entire screen unless it hits the opponent

A side problem I am also having is, i can summon my cannon an infinite number of times, when I want to only be able to summon one at a time