For the Footer Menu, please see the Social Links Menu documentation for the Exoplanet theme. The Trusted Pro theme works in the same way.
For the Primary Menu in the site header, add a Custom Link, write the link to your SM profile in the ‘URL’ text area, and then in the ‘Link Text’ instead of typing the word Facebook, use this code <i class="fa fa-facebook"></i> to display the Facebook icon.
See the screenshot below.
Other social media icons are also available.
In the code <i class="fa fa-facebook"></i> simply change facebook for twitter for example: <i class="fa fa-twitter"></i>
Some of the available icons (change ‘facebook’ in the code for any of these):
facebook
facebook-official
facebook-square
twitter
twitter-square
google
google-plus
google-plus-official
google-plus-square
linkedin
linkedin-square
instagram
pinterest
pinterest-p
pinterest-square
youtube
youtube-play
youtube-square
dropbox
flickr
reddit
spotify
skype
stumbleupon
tumblr
vimeo
vimeo-square
wordpress