My fan had a dual pole light switch... one for the fan, and one for the light. So the ceiling has 4 wires coming from it. One is a white ground, one a white wire, another red, and another black.
My light fixture has only 2 wires plus a ground. What do we do with the red, black and white wires?
Ground (bare, green or green/yellow) can only be a ground.
You need one neutral/return, and it must be a white or gray wire, so that's your white.
You need one "switched-hot" wire. Electrical code says you can use any color not already mentioned.** An often-used convention is that a switched-hot is the color other than black, i.e. red.
The remaining wire gets capped off at both ends. Put a smallish wire-nut (e.g. orange if you have it) and hold it on with a few loops of tape; as wire-nuts are prone to falling off single wires.
** outside of certain industrial installations. The general idea is that electricians should measure instead of assume.
