found the answer:
At the top of the page on the right, click Screen Options. Click the CSS classes button. Add the links to your social media items and put in the name of it in lowercase in the class box that appears after you add the link to the menu.
Default support by the css file:
google
vimeo
youtube
facebook
twitter
flickr
linkedin
pinterest
rss
i dont have the 2nd drop down named “Social Menu”, only “Main Menu” exists
I tried creating a new menu with same name “Social Menu”, and tried adding a link to it but its not showing up on the page
Theme locations: , Header Social is checkmarked