Your nearest test center is Magnormoen, easiest way to find the place is to search on Google Maps. The centre is open twentyfour seven.
If you are obliged to take a test, and are over the age of 18 you must also enter a travel quarantine. The general rule is that travel quarantine lasts for 10 days. You can take a PCR test no earlier than three days after arrival in Norway. If the test result is negative, you can end your travel quarantine.
Anyone over the age of 16 arriving from a red, dark red, purple or grey country or area and who is not fully vaccinated or have had COVID-19 during the preceding six months period should as a rule of thumb complete the travel registration form prior to crossing the border.
See all the rules at www.helsenorge.no/travel
At that website there is also information in many other languages.