In this section in Theme settings, you can add any and all links to the different social media accounts for your store. When they display, they will be an icon of the logo for that social media company. Any field that is left blank will not display an icon. Here are your options:
Make sure that you enter the whole url link with "https". Example: https://www.youtube.com/shopify
You can choose to display these in the Site footer, Menu drawer, or Password page.