Pass the battery cable through the opening in the new back plate.

Turn the connector head 180 degrees so the small white tabs are facing towards the mainboard.

Ensure the battery is correctly positioned and firmly press down on the base of the battery pack until you hear a click.

Check to ensure both case clips are engaged against the battery clips.

With the back plate loose, you need to carefully connect the battery connector and slide the metal bracket into its locked position.

This step is a bit fiddly but take your time and you'll get it to work.