How do you perform a fusion attack on Marvel: Ultimate Alliance 2?

I just rented the game, so I don't have a control bookletHow do you perform a fusion attack on Marvel: Ultimate Alliance 2?
Perform melee combos until your get a star in the bottom right corner. hold LT and and the letter of the hero you want to fuse with (A,B,X,Y).How do you perform a fusion attack on Marvel: Ultimate Alliance 2?
hold left trigger. if you are playing co-op, then that person has to hold left trigger as well. if you are by yourself, press a,b,x,or y.