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!