NTNU IT has produced a series of articles about printing at NTNU, you can find them here [in Norwegian].
In most cases, Mac OS X users visiting the library with their laptop computer with WiFi will find it easiest to access the printers by doing the following:
Choose System Preferences > Print & Fax
Choose IP printing
Choose “+” to add a printer
In the address field, enter the address of the local printer (typically xxxxxx.ub.ntnu.no, where xxxxx is replaced by the printer name)