Hi,
For most of the cases, it should adjust automatically.
To make the Facebook commenting interface responsive, place following CSS in "wp-content/plugins/super-socializer/css/front.css" at the end of the file:
#fbcomments, .fb-comments, .fb-comments iframe[style], .fb-comments span {
width: 100% !important;
}
Save the file back. Replace existing file, if prompted.