Lose all your pieces (or run out of moves) to win the game.
Antidraughts (or losing draughts) is a draughts variant where the objective of the game is to run out of legal moves. To win the game you must either lose all your pieces, or have your remaining pieces blocked so that they cannot move.
The rules of antidraughts are the same as International draughts, with the exception that losing means winning. There are no drawing rules other than threefold repetition (it is possible to end up in drawn endgame positions).