Since we're talking about BF2 (and I assume ranked) you probably won't have FTP access.
You should have a web-based control panel provided by your host, which allows you to access some of your server's game files.
In this control panel, you need to find the pb folder, and upload pbsvuser.cfg to it.
If this is all too complicated or your not sure whether you have access to these files, contact your host and ask them how to do it, or get them to do it for you.