How to find out more?

I have found the ship my grandfather, Amandus Åkenes, travelled to New York (from Kristiania) with in 1913. It was the "Hellig Olav". How can I find out which passengerclass he travelled on, how long he stayed, what he did in America, who he travelled with (if he travelled with anyone)? What can the passengerlists tell me and where can I find them? Hope anyone can answer this! Knut B. Lindbjör