Please follow following steps to add newly created FAQ page to your sites header or footer navigation.
Instructions:
1. Visit your stores admin panel.
2. Click on "Content" > "Menus" from left and side menu.
3. Click on menu where you would like to add "FAQ" page. In this case I would select "Main menu".
4. Click "Add menu item"
6. Hit "Save" on "Main menu" page and you should be all set. Navigate to your store