How do I use the srb2 server system???????

I really, really, REALLY don't know how to use it at all. What do I type when it says specify server address? The name or the IP? Around a couple of months ago, I was going to try to put the SRB2 server thingy where it just shows servers you can join, and that didn't work. Can someone just give me an explanation of how it works?