From Oslo city center: Take the Metro lines (westbound): 4 - Vestli, 5 - Sognsvann or 5 – Ringen to the stop «Ullevål Stadion». You will see the arena Ullevål Stadium on the left side when you come up from the platform. See map on the website.
The address is Sognsveien 77B. The Department of Economics are located on the second floor.
The front door, the lift and the stairwell are open.