Fusion is kinda complicated till u get the hang of it. first u gotta have 2 Portarra Earrings. You give 1 of them to the person you are fusing with, make sure you are on the same planet, post that you and some1 else fused on the message board, and il put your name here, with all your stats added together and times by 4. this can mame you very strong and comes in handy in some fights. When you take the earrings off, the person who owns them both again, and you can fuse again with any1 you want If you wanna 'defuse' then you have to post it on the message board. You can stay fused for as long as you want, but stats dont get added to your character till u take them off.
You can also fuse using the Super Portarra Ear Rings. Its same as normal earrings, except 2 times as expensive. it is worth it once you fuse because your stats get x10 instead of x4. You dont have to be on the same planet either. When they are taken off you get your stats added to each others characters and 1 Ear Ring back Each. Below is all the fusions so far:

Gokuhan
Mystic Yamgeta