The left column in Site displays all the navigation links your draft is currently using. Links that fall under the "Primary" navigation group comprise the main navigation. Secondary navigation groups (e.g., links in the theme's footer) are also displayed here. It is through this column that you control how site visitors navigate around your site.
Adding content links
To add links to a navigation group click the "Add links" link (shown below).
This will open the "Add links" sheet (see below) containing all the content that may be added to the navigation. This includes public albums and sets from the Library, theme templates, pages, social media profiles and RSS feeds.
In most cases, links to items are toggled on/off by clicking each "Add" button. After a link to an item has been created the button changes to "Added". Clicking "Added" will toggle the item's link back off again.
Adding link to current page
If the site page you want to link to isn't in "Add links", first navigate to the page in the draft preview. Then at the top of the preview window click the plus [+] button. Assign a label and you're good to go.
Adding links to outside sites
Click the "Add custom link" button at the bottom of the "Add links" sheet. Enter a link label and an absolute (http://) URL and your external site is now part of your navigation.
After a link has been added to the navigation you may edit its label, delete it, or assign it as the front page of your site. You do all these things by hovering over a link in the left column then clicking the gear button that appears at right. A menu will appear (see below) with each of the aforementioned actions. See the Assign a template as the front page tutorial for more information on that particular option.
To change the order of links in the navigation, click, hold, and drag any link in the left column into your preferred position.
Hiding the home page link
If you'd prefer to use your site title or logo to direct users back to the front page you can easily hide the "Home" link. Simply hover over the link in the left column that's marked as "(front)", then toggle open its options. Select the "Hide link" option (see below). To bring the link back simply repeat the process and select "Show link".
Add links to new template pages
In the "Add links" sheet you'll notice that some template buttons (when added) include an extra plus (+) button to their right, as circled below.
Clicking "Added" toggles the link on/off like normal, but clicking the plus (+) button does something unique. It adds a link to a new page using that particular template. This is useful should you want to create (for example) a dedicated page for albums assigned a particular category. Or a dedicated page for content assigned a particular tag.
If you want to learn more, head over to the Add filtered content pages tutorial for a detailed walkthrough demonstrating how to put these links to good use.