When you're happy with the fit and the wires, remove the backing of the foam tape.

Stick the battery holder on. If you're not confident with your soldering, solder on side before sticking the holder onto the board.

The tinned wires and pads will make it really easy to get a good solder joint and quickly attach them. Needle nose pliers or tweezers can help push the wires into the somewhat narrow contact recess.

After all four (4) wires are connected, trim the wires