Given the fact that there are now honestly shedloads of threads and people offering help on this subject, not to mention several wiki articles and forum threads which go into reasonable detail, and you're still UNABLE to find these, then I'm honestly tempted to suggest not running a server.
We could tell you to reset it and then reconfigure it from scratch, or attempt to guess the password.
Quite frankly though either of those options could land you in deep shit if you're not the "owner" or "administrator" for your kit - and if you were, you'd have no problem getting into it.
Perhaps you could use your brain and ask the person who set it up originally to configure it for you.
To hammer this point home, running a public, internet, server REQUIRES you to change settings on any router, firewall, or gateway device on the edge of your network. If you cannot control these, or have no access to them then just pick one of the hundreds of empty servers to play in.