Test out the new buttons on the PCB before reassembly.

Make sure that both the switch on the bottom housing and the corresponding switch on the back of the PCB are both set to the OFF position.

Attach the PCB back to the bottom housing, with extra caution when handling the battery coil wires.

Attach the mouse wheel to the PCB and bottom housing.

Attach the top housing back to the bottom housing by sliding the top pieces of the housing together.

Screw the screw from the battery compartment.