The following steps can be done by going to Design › Edit Theme › General › Footer › Social in your eCom back office.
This section allows you to enter the URLs for all of the social platforms that you want to link to from your website. Simply add the URL and it will display the corresponding icon in the footer at the bottom of the page.
If you do not want to display a specific social platform, simply leave the field blank.
You can also update Social Media settings via Settings -> Social Media in your eCom back office