Two player should grab the balls from the lions
The other two players without balls put trample steams down on the symbols with lions on them and face them at the tower.
The locations for these are in the spawn room, one located in the back area where you find the circuit box for the nav card machine, the other one is next to the two elevators near to the claymores, and another down one floor from the spawn at the bottom of the stairs.
Make sure they have been down correctly, if done correctly you will not be able to pick them up. The other two players with the balls should need to put their trample steams down on the symbols and place the ball on the trample steam before it is ready to be used.
The balls will be flung across the map simultaneously. At this point, Maxis will say:
"It is working, we are near our goal"