EFTA (Nordic Nationals)
The only requirement for Swedish, Danish, Icelandic or Finnish citizens planning to stay in Norway for more than 6 months is to report to the National Registry.
Report to the National Registry
The website of the Norwegian Directorate of Immigration (UDI) indicates that EFTA citizens (nordic nationals) staying in Norway for more than 6 months need to go to a tax office and show identification within 8 days of their arrival. More information is available on the website for Skateetaten (the tax office). Generally, you need to show a valid passport/national ID, proof of accomodation, and proof of a study offer when you visit the tax office. Read more about the documentation you need to bring to your visit here.