If you are using a official replacement battery this again should be a simple case of clipping the new one in place.

Finish up by replacing the restraining clip making sure to avoid trapping any wires. Replace the seat up by sliding it firmly forwards then screwing down

Alternative battery

Crimp or solder on suitable connectors for the new battery ensuring that the red and black wires are connected to the same connectors on the battery.

It is a good idea to ensure that the battery can disconnected for future diagnosis, external charging or replacement