Your replacement controller may not come with a power switch. If so, transfer the power switch from the original controller to the new one:

Unscrew the two Phillips screws on either side of the switch.

Reattach the cables from the new controller to the switch, making sure that they go back on the same sides you found them.

The white cable goes on the side labeled with the number 1.

The black cable goes on the side labeled with the number 3.