How do you replace the tail light cover on a 2005 Honda cr-v?

It will be assumed that you are referring to the taillight lens mounted on the back pillar.

Open the glass hatch exposing the screws that hold the plastic lens housing to the pillar. Un-screw them and carefully lift the lens housing away from the pillar exposing the wires leading to the lights. Un-screw the light bulb sockets about 1/2 turn and remove the bulbs from the housing. Re-install the replacement housing following this procedure in reverse.