You need to mark several areas on the floor. Usually, this is done with some ropes.
Mark sever areas that are parallel to each other. Each area should be a few meters wide.
All players start in the first area. They try to move other players to the next (second) area by pushing them to it. Each player who touches the floor of the second area has to move into it. The same activity is done on the second field: the players there try to move everybody to the third field, and so on.
There is no possibility to move back (from area 2 to area 1).
In the end, almost all players will end up in the last field. Only one player will remain in each of the other fields. The player in the first field wins the game, the player in the second field is second and so on.
Take care that nobody is hurt during the game. The players have to agree on some rules what is allowed (pulling, pushing, etc) and what is not (throwing people, hitting them, etc.)