Success!

I think the problem was the "Add CSS" field in the template customiser; I think it's actually meant for appending CSS instead of replacing it, so I replaced the CSS in the "View HTML" field instead.

I learned a bit of CSS while spending time editing it, so I can read it a lot easier now than when I originally started. Defintiely thankful for W3Schools and Liveweave (it's the first editor I found), as without those, I'd probably still be horribly lost.

Now that the blog's themed, I can finally work on the content.

(Edit) Oh right... I was supposed to put in a custom font... I'll do that later.

(Edit 2) Had to fiddle with the CSS again once the fonts were in place, but I think it looks decent enough (plus, font sizes are wonkier the CSS way than the old HTML way).