How is secondary nav implemented in Source theme?

I’m still learning the ropes with Ghost, and I can’t figure out how the secondary nav for the new Source theme (shown below) is achieved.

Does it require template modification, or can it be done from the post / page editor? I assumed it was built-in functionality since it’s the default theme, but I can’t figure out how to access (or implement) it.

Thanks for any info or insights.

In the navigation settings within your admin area there are two tabs - “Primary” and “Secondary”. The screenshot you’ve posted is how Source uses the primary nav, the secondary navigation is used within the footer like this:

Docs for navigation can be found here: