So I have been playing this game for way too long now but there is one thing that I still cannot figure out.

Certain moves with certain characters like Chun lee need to do some sort of charge to do moves. Chun lee's version of a fireball requires a charge before a punch (if i remember correctly) but the thing that is never explained is how to charge. The game just automatically assumes you know how to charge.

Does anybody know how to charge?