I wired the fan to the ceiling box, white to white, black to black and ground, there was a red wire I put a plastic nut on it and tucked it back, I didn't use it, I hope I don't need it. The problem I am having is wiring the wall transmitter. The on/off switch has one black wire on the top screw and 2 black wires connected to the bottom screw, which one do I connect to the black power wire to, and I don't see a ground wire on this switch. The wall has 3 on/off switches. One of the other switches has a ground wire, can I connect to that.

Your ceiling box has black, red, white, and ground? Is the black hot, or switched hot? What was connected before? Does your fan have a light? Is the ceiling box power controlled from one place and one switch or two places? Or two switches? Sorry for all the questions. The switch you are describing sounds like it is a "3 way switch" allowing control from two locations. Let us know more. It might be easier to get a transmitter that fits under the canopy of your fan.

2 black wires connected to the bottom screw

One of those two wire will be the power coming to the switch. The other will be taking that power on to something else. However, you are not permitted to have two wires under one screw. Often you will see that the electrician remove some insulation about 6" from the end of the wire. Then put the bare section of wire under the screw and connected the end of the wire to another switch. That is permitted. If you truly have two wires under one screw, remove and put back together with a wire nut and add a pig tail.

The other single wire on that switch will be taking power out of the switch, presumably to the fan.

How you will wire this device depends on two things. Whether you intend to keep the switch and whether the device actually controls the operation of the fan. In other words is the device really a transmitter that send a radio signal to a receiver in the fan which controls the fan operations, or is it really a receiver that gets a radio signal from a remote and controls the operation of the fan.

Yes, you can use the ground connected to the other switch.