This token allows the theme to securely access your Instagram profile, for the sole purpose of displaying your Instagram photo feed in your shop.
By clicking the button on the left, you'll be prompted to log in to your Instagram account and authorize Out of the Sandbox to access your Instagram photos. Then you should be given a code that looks like a very long string of numbers and letters.
Once you have the token code, you'll just need to copy and paste it into your Social Feeds section (under Customize > Sections) along with your Instagram username and you'll be all set!
If you are using a theme that has not been updated since January 2018 (older than Turbo 2.2.3, Parallax 3.3.4, Retina 4.2.5, Mobilia 5.3.3, and Responsive 6.3.3) and your Instagram feed is not working, you most likely need to update your theme before generating a new access token.