Instagram icon Casper

I’m trying to create an instagram icon, like the facebook one in the right corner, and found this guide Tutorial: How to add social networks to your Ghost site
However I have no (or cannot find the) site-nav.hbs in my Casper Partials. Am I missing something or is the guide out of date? I’m simply looking to create an instagram link as an icon in the right top side instead of as text with the other secondary navigation.

Appreciate any help

I am also interested in this topic. Indeed, the Tutorial should be updated, because the site-nav.hbs is not present in Casper theme anymore.