Please follow following steps to add newly created FAQ page to your sites header or footer navigation.
1. Visit your stores admin panel.
2. Click on "Online store" > "Navigation" 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"
5. Enter a name you would like along with your FAQ page URL. After you copy paste FAQ page link, it would show you like below so you need to click on link above "No results". Make sure you click on link above "No Results".
6. Click "Add" and then hit "Save" on "Main menu" page and you should be all set.