By clicking on your username on the upper right corner you have a dropdown menu that gives you access to My profile section, which contains the following options: Change info, Change password and Avatar .
In the Change info section you can change the first and the last name corresponding to your EmailTree account.

The E-Mail Address field cannot be modified.
The Department field allows you to delete or add new departments by using the select menu.

Click Update to save your changes. A message confirming the update will appear above the Change info section.