How can I?

Team attacks are bad. In a Team Brawl, you turn the option on, and you and your teamate(s) can attack each other. The use for this is to be cheap and fly solo in a Team Brawl, so your enemies do the dirty work for you. Btw, don't do that, cause your friends wont want to play anymore.

I think it's in the more rules section, BUT WHY WANT IT. You are in a team!!!! IF you accidently kill your team mate, not just that he losses a point but you lose two. I tell you that is evil. Don't do it, or else..........

If you mean so that you can attack your partner it's in the rule section. Thats not a very good idea to attack your partner though. I doubt you would want that so I think you might want to know if you can team up and do an attack. If so then you can't do that. You could set up an opponent for your parners Final Smash but you couldn't really have a team attack.

You have to get 200 kos in brawls. Then go to the additional rules section in the rules manual and there should be team attack.

You have to unlock the Additional rules option and in there
You can turn Team attacks on or off.

If you wan't to set up your friend or someone then this is the perfect thing to set on,it lets you attack.on the other hand if you kill him you are losing lives so it's very doubtful you will win