Navigation
Adding a Header and Footer to your site.
Every page has a layout by default. This is the portion of the page that is consistent across your site. Generally it's a header with a navbar and a footer with a copyright but you can get creative.
Editing Layouts
Let's start by editing the default layout. In the Content tab, choose Layouts from the sidebar and open the default layout. You'll land on something like the page editor, but with two slots for blocks instead of a one.
The header slot is for your navbar and the footer is for the copyright and stuff at the bottom of pages. Add a navbar block from the library to the header using the plus button. You can select the block and edit the logo and its links. Adding a footer with links is the same thing, select one from the library and fill in the details.
Changes you make in layouts happen on every page that uses the layout.
Alternate Layouts
If you have a section of your site that's different you can have an alternate layout. We use this feature on this site to add the sidebar with links to the documentation pages. Create one the same way, then assign it to a page with the Page Layout field in Page Settings.