You can add a social media block to the footer of your newsletter, with icons that link to your social media accounts. To add the social media block, open the content elements block from the "+" sign in the bottom left of the page, then drag the social block to where you want it in the newsletter.
A default block appears where you dragged it. To change the icons and their links, click on the settings icon in the top left of the social block.
On the right side of the page, the settings window of the social block appears. You can choose the icon styles from there (big, small, round, rectangular etc). Then you can add links to your social media sites (1) and then click on "OK" (2). Those icons, for which you filled out the URL address, will appear in the block. If you want to remove an icon, delete the associated URL address.