Starting Server on linux

Let me start off by saying I am generally a PC user when it comes to servers, so I hardly know anything about starting a server on linux.

The only reason I am actually starting a server on Linux is because, well, my stupid Vista refused to work for me when starting a server on PC.

My questions are quite simple… I have downloaded all the content, and my server is supposedly started through terminal. I get the text

“Starting up Garry’s Mod 10 server.
Started. Type screen -x to resume!”

My questions:
1: When I type screen -x I get the text “There is no screen to be attached.” What does this mean/how can it be fixed?
2: How can I connect to my server? Do I need to port forward like has to be done on PC?

Thanks for the help in advance :\