Geneva is a small city and the University is within walking distance from most hotels in town.
From the Airport, you can also take the train to Geneva Central Station (first stop). It is the same price as the bus but the train airport station is a bit further away than the bus.
You can use the same ticket on the bus or train. It cost CHF 3 and gives you free ride for 1 hour (with possible connecting buses). You must buy your ticket before getting on. There are machines at every bus stop. But you need exact change. On the otherhand, the ticket machines for the train should return the change. You can also buy in newspapers kiosks a multi-ride card for CHF 20. You can use to pay your ticket on the automatic machine and it will be useful for the whole week in Geneva.
Finally, you can also take a taxi. It is very expensive considering that the airport is about 5km from the center.
If you arrive by train, or if you reach Geneva train station (Gare Cornavin) from the airport, you can take a tram (e.g. tram no 13 goes near the University), or you can even considering walking to your hotel. Of course, taxis are also available but again are an expensive way to move in a rather small town.
If you come by car you should make sure your hotel has a parking place. There is no easy way to leave your car in Geneva.