The center terminal connectors go to the lift motor. One will be a ground conductor and the other will be a 12 vdc positive conductor; controlled by the switch. It does not matter which way your switch is directed for the rest of identification of terminals. One corner will connect to a frame ground source and jumpered to the directionally opposing terminal. The last two opposing terminals will have the 12 vdc positive conductor connected to a fused circuit from the positive post of the house battery; (you can pick up power from any sufficient rated but not fully loaded circuit).
Summary: two center terminals are the load and the outside corner are the power supply that can change the polarity to the load when the switch position is changed. BTW, the switch should be a momentary double pole double throw.
PS: If your switch is labeled and the direction of the lift is reversed; just reverse the two center wires on the switch, going to the motor.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7