When customizing your theme, by default, the social media links placed on the footer are populated with a placeholder URL so you can add your own links.
To add your own, navigate to the Customization tab and click Customize. Then under the Theme home page option, under the Storefront home page section, click Customize page.
On the navigation bar on the right, select Footer. Then, you will find the social media icons and links. replace those links with your own and click on Save.
If you would like, you can also remove the social media icons on the footer.