You generally need an electrician to install a bathroom exhaust fan.
The installation of a new fan will necessitate the running of new wires, and it is recommended that homeowners avoid attempting any electrical work themselves for their own safety and the protection of their property.
These days, most bathroom exhaust fans also function as lights, so you can clear the air and brighten the space without sacrificing either. Call an electrician if you need a new bathroom exhaust fan installed or an existing one replaced.