I used a pre-made site but I cannot figure out how to edit it the way I want. I can't seem to delete pages that were pre-made, or edit the HTML. Is that specific enough?
Editing HTML with Google Sites
Google offers instructions to edit pages and HTML. Here's a summary from that page:
You won't be able to edit the full HTML of the page template, only the inner HTML relevant to the content on that page.
You can also insert HTML boxes containing small snippets of HTML if you need to embed external content like a presentation on a page.
Deleting a page
Google's help pages have instructions to delete a page. A summary: