this achievement is pretty easy
just grab a buddy or set up a session on here and create a club
once the club is set up both players go to the match lobby and in the settings change the game type to league
make sure someone plays as position any so that someone can control all the players rather than just 1
then obviously just keep playing games until you win 1
i teamed this achievement up with the at the top achievement in a nice and easy video guide below :)