First and foremost you can"t add a standard exhaust fan without the express permission of the landlord (in writing) .  A temporary exhaust fan can be installed in the bathroom window (fits under the window) It uses a standard AC plug.....If you get the OK you will then need a Licenced electrician to install a switched service line .  It is assumed that bathroom has an outside wall for the fan"s installation. If it doesn't You would have to be on the top floor AND the Landlord (owner) will have to allow roof penetration (rare) .....  lots of luck