How do you use Vegito after unlocking fusion?

[Titan]

Title. I've done the quest to unlock fusion for Goku and Vegeta post game, but unlike with Gotenks I cannot see any fusion move in the list of support moves for either Goku or Vegeta. How do I activate fusion with these characters?

[Crimsomrider]

You need to equip the transformation just like any other and then have both Goku and Vegeta in your party, which will allow you to transform into Vegito while in battle.

Keep in mind it's a transformation, not a support move, since they're main characters.