To add social media channels to your site, from the store dashboard go to:
> Store Settings > Store Settings > Social Media

From within there, copy and paste the URL of your 'Facebook', 'Twitter', 'Instagram', 'Pinterest' and/or 'Youtube' profiles into the corresponding fields and click 'Save Changes':
The URL is the address of a website. You can find it in the address bar of your web browser:

(*Don't forget to click 'Save Changes' after making alterations*)