Now that everything is free you can remove the battery. Its held in place by a glue strip on the back so you need to be careful when pulling it out

I found it easiest pushing dental floss under the battery on the upper side and then carefully pulling lengthwise to cut the glue. This way you reduce the risk of bending the battery when trying to pry it out.

When pulling the battery out, pull it out on the side marked with the red arrow, as the other side is held in place with notches(yellow)

Remove the marked(green) foam Pad to put on the new battery.