No Navigation in Categories/Tags?

Hello, I’m testing this theme out on my blog (I love it), but when I click on either categories or tags, there’s no navigation to more posts. I have my blog set to 4 posts per page, but that’s all that seems to show up when I click a specific category or tag. Also because I only have 4 posts, my page is on the short side, and for some reason the bottom of the page shows white instead of the background colour. Is there some way to fix that through css (I can’t find it)? Thanks.