Player vs player, how do i play my mate

Me and my mate have both got teams on seperate files and would somehow like to play my team vs his. Is this possible in any way?

You can't play more than 1 save game at once or use teams from one save game in another. To play your mate, you will have to start a new game and add 2 managers in so you can both play or play over a network

Use an editor to turn an unused team in one of the games into an exact replica of one of the player-controlled teams?

Then both teams will be on the same file. Add a user to be in control of the newly created replica team. Then play the teams against each other.