Well, perhaps you should read the whole Wiki.
Alt.Binz doesn't dopwnload headers from groups, it only handles NZBs and search results from integrated search engines. Xpat is a special server-side search that's only supported by certain providers - and in any case isn't something you should use often if at all. So you can completely ignore the Newsgroups tab.
Instead, use one of the search engines. Newzleech, Binsearch, aEton allow you to browse groups. Follow the Wiki for instructiosn, but in brief: Newzleech -> click Search button once to retrieve group list -> pick group from dropdown list -> click Browse button.
The real power of Alt.Binz lies in searching rather than browsing, though. Because you don't have to fetch the headers for each group, you can search across all indexed groups in an instant.
You'll soon get the hang of it. If not, there are plenty of other clients out there.