The venue can easily be reached by public transport:
NS Train to Amsterdam Muiderpoort, +- 900m walk. 2.10 €, single ticket can be bought from the vending machines or counters in the train station. If you're traveling from Schiphol Airport, buy a ticket to Amsterdam Muiderpoort from Schiphol (3.90 €, train runs every 30 min direct, with change more often) rather then buy a second ticket at Amsterdam Centraal. (walking directions, ns.nl schedules).
GVB Bus 22 to Zeeburgerdijk +- 300m walk. 2.80 €, single ticket can be bought on board of the bus.
The dorms tend to consist of bunk beds where each bed has its own light and power supply. Inside each dorm there is a separate toilet and a separate shower. A sink is available in the dorm itself. You have to bring your own towels or rent them at the hostel.