1. Read me file is the staring point. It includes some guides and FAQs which answers most of your questions. So you should start reading now if you haven't.
2. Choose a layout based on how much content you have, make it empty so you can start writing your documentation content.
3. Navbar is a must have components for most of websites. Lean about navbars to create your own or use any of the available samples by visiting navbar documentation.
4. UI Kit is the final destination for your creativity. You can use those components to write your page content. Make sure you'll take a look at the content even if you don't read all at once, so you know what tools you have.