Help!

[Modesty]

A guy that work on site of the company where I work has quit and now I have to work on it. I have a little experience in web design, but the site has forum and I have never been working with forums. So, I know my question is probably stupid, but I have to ask. How do I login to forum as admin? I don't have his password and I can't contact that guy (which was admin), but I do have password for the site. So, the question is: can I in Dreamweaver change what I want, delete unwanted posts etc? Or can I, I don't know, find I document on the site where that password is stored?

Thanks in advance, every help is welcome.