From your admin panel, locate the "Appearance" label in the left module, hover your mouse on it and click "Customize"
Once the customizer has loaded, click the "Social" label in the left panel.
There you will find a list of several social networks. Locate the ones you want to add or edit and change the link. Leave blank the ones you don't want to use.
Don't forget to save the changes by clicking "Save & Publish" on the top right of the module. All set! You can close the customizer.