How to change remote key battery?

cost is a couple of $ for battery; open the key gently with soft pressure on sides (use something sharp) remove the battery which is i guess the same in all keys CR2032 you'll see the battery comes on a loose component tray.
remove and replace the battery make sure rubber seal is in place properly on bottom keyring and reinstal the battery tray in the button side of keyring first(top part) snap down in lugs, then push in bottom part of keyring and hey presto! bob's your uncle and you can open your car again.
i hope i make sense this is the first time i try to explain something like this!

ps do not try to force the two parts together if you just drop the battery tray in bottom part of keyring i have done this before and wrecked the plastic lugs!