Adding a Custom Social Media option

Hi, Anyone know how to add my own Social Media option (such as Instagram) in addition to the ones that come with Sento theme?

I am currently creating a Child Theme of Sento. I’ve been looking around the function.php but I couldn’t find any function that defines the social media.

I saw a function that somewhat define the social media in header.php (<?php echo thinkup_input_socialmediaheadermain(); ?>), but I couldn’t find that function in function.php.

Anyone could help?

Thanks!