You put the forked side in the gap. You tension the screw onto the top of the bolt.
With a modest amount of tension applied, you whack the side of the knuckle and should hear the ball joint pop. You might have to repeat a time or two but once you get the hang of it you will appreciate the tool. Welcome to the rust belt.

__________________
2001 x5 3.0 (sold with broken motor), 1990 e30 M3, 1991 318is, 2002 325i, 2008 335i Dinan stage 3 6 speed,