First, be sure that you have a full momentum meter. Then, irish-whip your opponent into your teams corner. Then, walk up to the cornered opponent and press the button which activates your finisher. Then, as long as your tag team actually has a tag team finisher, you'll do the finisher.
Brawl FC: 1891-2896-6944
Rich's first ever Super Smash Bros Brawl Wi-Fi Opponent