To add a user as an admin in the control panel under whatever "member management" wording there was should have a link to "add user" (I think it's at the bottom of the page).
It's about as cryptic as it gets, as UBB.Classic was shelved in 2007; you should consider getting yourself on the latest UBB.Threads as there have been loads of feature changes and threads will be significantly faster than classic (and there are people around who can support it).
