SharePoint 2013:
Editing Users' Personal Information
As
the SharePoint Administrator of your SharePoint 2013 site, it is
important to edit your users' information. You have the ability to
change everything from their first name to adding a photo to their
profile. In another case, what if the users email has changed; you can
also change this as the Administrator.
To follow along with this example, you will need to log in to your Tenant Admin site. Simply append /admin to the URL of your site (for example: https://company.atrackspace.com/admin). You cannot complete the following steps from the Root site. Further, not all users have access to the Tenant Admin site; please talk to the Site Administrator for your tenant to gain access.)
1. From your tenant admin site click
Manage User Profile Application.
2. On the Manage Profile Service page under People click
Manage User Profiles.
3. On the Manage User Profiles page type the users name in the “Find Profiles” box and click
Find.

4. Scroll over the users Account name and click the
drop-down arrow.
5. From the drop-down click
Edit My Profile.
On the Edit User Profile page it is important to take note of all of the different fields you have the ability to change as a Site Collection Administrator.
6. Once you have made the changes you wanted BE SURE to click
Save and Close so your changes are saved.

Its as simple as that!