Check the wiring to the switch. If you are not getting voltage there, then check it at the fuse. If you have voltage leaving the fuse it is a broken wire.
If you are getting voltage at the switch, turn the switch on. If you are not getting voltage through the switch it is a faulty switch or switch connections.
If all that checks out Ok, check the voltage at the fan motor with the switch on. If you are not getting voltage at the motor it is either a broken wire or poor connection. If you are getting voltage at the motor shut the switch off and check the fan motor leads for continuity. If you are not getting continuity it is a burned out motor - throw it away and get a new fan.
If you don't know how to do the above you shouldn't screw around with it. Just get an electrician.
jack L