You are able to take: taxi, bus and train. It depends on what you prefer. Taxi is expensive in DK but quick. When you use bus or train, you can buy a 10-tour card or a Copenhagen card, depending of how much you want to see and use public transportation. It takes approx. 1-1½ hour with bus or train from the airport. 30th September 2019 the Metro Cityring is starting, so it is far quicker to get to the apartment then.