To understand how NZB files work, I will first explain something about posts on Usenet.
Every file on Usenet is split up into many separate parts. These parts are called articles and are combined again to one file by your newsreader after downloading. Each article has a unique number, the so called message ID. With this number your newsreader knows exactly which file to download, because there is only one file with the same number.
An NZB file is a collection of message ID’s of the files the NZB has been made for. These message ID’s are combined in a text file with the extension .nzb. I you have this .nzb file, import it in your newsreader (see the tutorials for each newsreader supporting NZB file on Binaries4all.nl) and start downloading at once.