Upvote:1
You will clear immigration controls in Amsterdam in any case, because the flight from there to Norway is an internal flight.
To get to the city of Amsterdam, when you arrive in the airport, follow signs to the airport exit. You will pass through immigration, then the baggage claim area (where you will not claim your bags) and customs. After passing through customs, you can follow signs to the train platforms, where you can buy a ticket and board a train to Amsterdam.
When you return to the airport, you will need to clear security, of course, but not immigration. Follow the signs to your gate (check the monitors in case the gate printed on your boarding pass has changed).