7
Yes, you can create your own pages, or install a forum - or pretty much anything that a module exists for.
The best suggestion is to take a look at some other sites powered by XOOPS - and see how they tick.
For example - if you want to build a community site: install a forum (cbb would be a good one.. although I may be biased on that!), a gallery module for people to add their own images, and a news module ... that would make a good starting point for your site.
if you get stuck... please feel free to ask here. (Although many questions can also be answered simply by using the search in the corner)