how to add a social icon on my header

at the very top of the web, there is the company’s logo, a search bar, phone number and a few social icons.

just took the website on my hand to help edit. Not sure if it is about the theme or list. I have gone through all the options I could find on the dashboard but I still could not find where to add an icon or change the number.

I would like to add a number on desktop version, and add an icon on phone/tablet version.

Could anyone kindly advise the way to get to the place that i can change anything. Thanks a lot!!

The page I need help with: [log in to see the link]