The wysiwyg editor isn't supported in Tiki 1.9.7, and in 1.9.8 only works for blog posts, not wiki pages, as far as I can tell. In 1.9.8 it works without additional steps AFAIK. The editor I think works also for wiki pages in Tiki 1.10CVS, but this is a development branch and so is unstable, and I'm not really sure if the editor is 100% even in 1.10.
Anyway, I'd upgrade to 1.9.8 to at least get the editor package and the (limited) functionality that's built into that (stable) version. If you want wysiwyg editing for wiki pages now, you'll have to risk using the development version, which may be partially or fully broken at any given time. (A stable 1.10 release is planned for Real Soon Now(TM), but there's no word on exactly when.)