To enable the Instagram feed, navigate to Footer → Instagram Feed.
For the Instagram feed to work, the plugin Smash Balloon Instagram Feed needs to be installed and active. If it isn’t, the following message will be shown:
Simply click on Install & Activate plugin. Once the plugin is installed and activated, you need to connect your Instagram account.
Go to Instagram Feed in the the WordPress Admin and connect your account:
Now you can set up your Instagram feed from the Customizer: