How to Put Mutual Friends on Facebook
When you request to add someone as a friend on Facebook, the Web application automatically detects any users that you may know. These mutual friends are added to your Facebook as a friend using the "Add as a Friend" button. When the recipient of your request sees your message, any mutual friends are shown. This helps people identify you as someone they know.
Open your Web browser and go to Facebook.com.
Type your Facebook user name and password and press "Enter." After the application logs you in, your Wall is shown.
Click the "See All" link in the section labeled "People You May Know" on the right side of your page. This opens a window with all the people you may know. This list is generated from your own friends, so these people are typically mutual friends or family members.
Click one of the people in the list. Click "Add as a Friend" to send a friend request. You must wait for the person to accept you as a friend before you are added to the mutual friend list.