You will need a very small (watch or glasses) Philips head screwdriver, and a SR626SW (or know as a 377) watch battery.
Remove screw 1 to remove the motorcycle back cover.
Remove the other 2 screws to take off the clock backing.
Remove the white plastic ring by pulling directly up.
Remove the battery.
Put the new battery in.
Press the white plastic ring back on.
Reassemble the clock backing with the two screws.
Reassemble the back of the motorcycle with screw 1.