When you use the Fusion Technique, you will need to have learned the technique. You will also need you and another person from the RPG that has the same technique.  When you fuse you will need to pick a name for your new character.  This can be a name already exsisting, if you fuse the right characters to make this name. Or you can make up a name that doesn't exsist.  Using the Fusion technique will take up one turn in a battle.  There will be no fusions before a battle unless otherwise told by an owner of this site. 

ALREADY MADE FUSIONS AND NAMES
Goku & Vegeta = Gogeta or Vegetto
Goten & Trunks = Gotenks
Piccolo & Kame = Kamicollo

EXAMPLES OF MADE UP NAMES

Gohan & Frieza = Gohieza
Piccolo & Krillin = Krilicollo