How do I fix the content of my homepage so that it doesn't change?

You can "stick" any single blog post to the homepage. When you do this, the content for that blog post shows up on your homepage as normal content and not as a blog post. It's not taken down until you unstick it. So, you can still write your blog and it will all flow chronologically on your blog page without changing your home page. Read how to stick and unstick posts to your home page.