How do I uninstall a ceiling fan?

Turn the power off, to be safe i recommend turning it off at the breaker box, there should be a list on the onside of the panel door showing what switches operate what. or you can simply leave the wall switch that operates the fan in the off position if you're sure nobody will turn it on. If fan has a light remove the glass bowl over the bulbs, should be three screws it the top of the glass fixture, loosen them with your fingers, if they are to tighttry pushing up on the bowl from the bottom to relieve pressure off the finger screw. Remove light bulbs then unbolt each fan blade, once the blades are off remove the motor cover should be one small screw at top of the cover close to the ceiling, once the screw or screws are removed if the cover does not come down you may need toturn it using both hands, it only needs to turn a little bit and no need to be gentle. With the motor cover off the mounting bracket should be easy to spot. Some brackets only have one srcew on one end and a tad that slides into a slot on the upper bracket, by removing the one screw this will allow the motor assembly to swing down but still be attached to the bracket for support. Whith the motor hanging the wiring in the fixture box in the ceiling should be visible, pull the wires out of the box so ythat the wire nuts are accessible. there will bee three wires coming from the fan, one screwed directly to the box or bracket, loosen the screw with a screwdriver and pull the wire from the box, the other two wires attached to wires with wire nuts, one at a time remove the nuts by twisting them off with your fingers, pull the wires apart and twist the wire nut back onto the wires coming from the box in the ceiling, the fan should now be disconnected. romove the motor from the brack by turning it 90? and sliding the tab out of the slot in the upper bracket. remove the upper bracket piece from the fixture box. Now that you have done this installing a new light fixture should bea breeze for you.
the video shows a different easier type of fan removal. There are numerous types of fans and how they are mounted, i hope this helps you