The main University campus is situated to the south of Manchester city centre either side of Oxford Road (University buildings shown in purple) on this map. A more detailed map of the campus, including a number key for all the different buildings can be found here. And the interactive map is also useful.
Information about transport is available from the University webpages.
Manchester airport, to the south of the city, is the nearest airport. There are regular trains from the airport to Piccadilly and Oxford Road Stations and taxis cost around £20 from the airport to the University.
For those driving, see the details from this link. There are a number of car parks on the Oxford Road site.