Reach up behind the light and unscrew the two nuts holding it on. Pull it out, take out the bulb sockets (with the bulbs attached) and there you have it, in your hand. Then reverse the process with the new talilight! WALLA, go riding!!
If there is a problem with the inside of the light, remove the two screws on each side of the lense (from the rear) to remove it from the light assy.
You should have two bulbs lookin' at ya.