There is a rubber strip stuck on one side of the OEM battery, protecting the printed circuit board from the battery,.

SAVE THIS PIECE. It is a crucial component to prevent battery damage.

Separate it from the white housing, and replace it onto the replacement battery.

Install the new battery, rubberized side facing the printed circuit board, and apply a replacement adhesive strip on the other side of the battery to keep it stuck on the outer frame.

When ready, unplug the old battery from the circuit board, and install the new battery's cable.