You just move the thing.
I dunno the name for it either, but flip the plastic square thing that hits the switches under the stick. You can move the stick to the diagonals but it should only hit 1 switch at a time.
I was trying to be as vague the OP until he shares enough information to warrant a real answer.

The part you're thinking of is called the actuator, but flipping it only works on Happs & Happ knock-offs.
A sanwa JLW would require loosening and turning the restrictor plate.
A sanwa JLF would require turning the center part of the restrictor plate.
A seimitsu (and knock-offs) would require unscrewing and moving the plate on the bottom.
A lot of the old sticks had completely different actuators for 4 or 8 way operation.