How do I use the NZB's on this site?

I'm using a grabit and I'm an extreme noob at this, I just grabbed a random NZB from http://filesharingtalk.com/nzbs/ and I open it using grabit and come to this screen ( http://i55.tinypic.com/qxs8k4.png ), what server am I meant to use? Do I need to pay to use the NZB's on here? :p

Thanks in advance, looking forward to being able to download some stuff and contribute some stuff of my own.

You need a news server to do anything with those NZB file. Like astraweb for example, which is quite affordable.

Some free servers exist also, but I never looked into them.

Take a look at this: http://filesharingtalk.com/threads/384765-Noob-s-guide-to-usenet

You can find some free servers, look for the binload thread here and IPv6 tutorials, also on this board.

I think Just4Today would be fine to learn the basics of Usenet by doing. The service isn't outstanding, but you won't need to bother with IPv6, for example. Consider it a "demo" of the real thing's full awesomeness :)