Well... that's kind of a vague request, but I'll try to help, and someone else can fill in the gaps where I'm not knowledgeable.
There's three kinds of ways to play multiplayer: LAN, Internet, and Gamespy.
LAN is playing over a local network. If you've got more than one computer at home, then this is probably a good choice if you're playing against someone in your house. I don't know much more about it than that.
Internet is connecting to another computer to play, but you have to know what computer you'd like to play with. I'm really not knowledgeable in this area either.
Gamespy is a matchmaking service inside DS2 that lets you join games with strangers (who then can become friends, or axe murderers). Each person on Gamespy has an ID (not the same as a character name, though), and after selecting which of their characters they'd like to play as, they're taken to a list of servers named from characters in the game, like Rahvan, Xeria, Azunai, Dalziel, and so on. Finally, after joining that server, you'll see a list of games on that server (sometimes there aren't any). Double click on one you'd like to join with your character.
Now, don't expect too many people to be playing at one time. Not many people do play multiplayer DS2. You might be better off playing with friends or doing only solo play.
Oh, and welcome!