Carefully pull the back off. Keep an eye out for the C/F switch that is held in place by the bottom cover. Don't pull too hard or you may break the wires from the battery compartment.

Set the plastic C/F switch in a safe place as it bounces away easy and is small.

If you need to completely separate the cover from the case you will need to unsolder the wires to the battery compartment.

To reassemble, put the C/F switch in its spot and press the cover back on being careful not to pinch wires. Reinstall the 4 screws.