Attach or remove a contact to/from a list
Go to the My Contacts tab and search for your contact. Once you have found your contact, check the box to the left of the contact to select it.
Once you have selected your contact, go to "More options" and click on "Add to static lists" or "Remove from one or more lists" as needed.
A window will then open. Click on the box to display all your previously created lists, then select the desired list. For information, a contact can belong to several different lists.