From the Contacts page, find the contact you wish to edit and click the contacts' name to open up their detailed information.
In the contacts' information window, select Edit Contact in the upper right hand corner. Make any changes to the contacts information and select Save. Or, click the Delete Contact button to permanently remove the contact from your Studio.
Related
From the contact detail page, you can also:
View the contact's activity log and add internal notes (see the Contact timeline article)
Clear an email suppression if their email has hard-bounced (see the Suppressed contacts article)