first for goku and vegeta to turn vegito get 3 number thingys under your character picture then hold the analog stick with the 1 hold the analog stick pointing < with 1.it will take a bit long so hold on it as long as you can until your character jumps out and with vegeta.

PS do not EVER EVER release the anolog stick pointing to the < and 1 until they do the fusion
it worked for me and my brother