Place your new battery in the vacant battery spot and lean it forward to get access to the wires as pictured

Connect the wires to the battery exactly as they were removed. The wires will stay in position and should line up with the correct terminals

Lay the battery flat in the cartridge so it is flush with the others. If your having trouble getting the battery to sit flush in the case then a corner may be hung up on one of the wires, just shimmy the wire to the side.