There are several options from airport to hostel. The 370 and 197 bus bring you directly from Airport to Hostel (get off at Van Gogh Museum, return ticket cost 10 euros). You can also take train to Station Zuid then change tram 5 (get off at Van Gogh Museum)
From Amsterdam Centraal station:
You can take tram 2 or 5 and get off at Van Gogh Museum.