HOW TO GET HERE
The visiting address of NORDITA is Roslagstullsbacken 23, on the same Campus as the AlbaNova University Centre. On these pages, you can find some detailed descriptions for various ways of getting here.
A short version is also available to download, together with a map showing you how to walk (if you don't take the bus).
Check out the web page of the local transport of Stockholm (SL) -- which runs tram, subway and busses -- for a detailed explanation of their fares and tickets system. The best option for you would probably be to go for a 7day card. Note that tickets cannot be bought on the busses!