Take the green line north (remember to enter the train in the front) for two stops to the station called Rådmansgatan. Follow exitsign marked "Handelshögskolan" and then take the stairs up on the right to "Sveavägen". When you come to the top, you will be on "Sveavägen", and "Rehnsgatan"will be direcly to your left - you will see the Hostel stright across from you on the other side of Rehnsgatan.
By plane: From Arlanda, you can choose to take the flight bus or the Express train. The train is more expensive than the bus, but makes the journey in about half the time (20 minutes instead of 40 minutes.)
Bus goes to the City Terminal (Stockholm) and the express train goes to the Central Station (Stockholm).
From other airports
From Skavsta-, Västerås and Bromma airports, you can also take a flight bus to the City Terminal (Stockholm).
Hostel Bed and Breakfast, Rehnsgatan 21, Stockholm, phone 08-15 28 38.