Normally, one is for the (internal) float and one is for the pump motor operation. While they may be operating from the same outlet, they are controlling two different things. If you just plug in the one that controls the motor, it should run continuously. Many sump pumps have a separate float that is connected outside the pump and "flips" the motor on and off at certain positions or heights.
If you have never made a mistake, you haven't done much.