2
It's not a stupid question at all.
Content is added mainly through blocks and/or modules. Try out the blocks for yourself in the admin side to discover what you can do with them
For the homepage, you can either set a module to display it's content (which is an option in admin->preferences->general settings) or add blocks to the page (admin->blocks).
If you need more than just placing custom blocks of content on your site, you should look for a module that serves your purpose. There's heaps of them, for news, photo albums, articles, downloads, links.. just take a browse through the module repository here to find what you're after.
Some links to help:
Xoops for dummies: a terrific resource to learn about Xoops
Official docs: which Carnuke has temporarily made available for download on his personal site, as the offical docs.xoops site is currently being rebuilt.
JDSeymour's tutorials: excellent Flash tutorials
Hope this helps
Rowd