Just to let you know, you can only do these things if you are an account administrator or above.
On the Home page, click on the settings icon. From there click on account. Click on the people tab.
Click on the icon which will take you to the user's profile.
Click on the icon and you will then need to enter the new email address in both section as well as your current password.
N.B: An confirmation email will be sent to the new email address, the previous email will be no longer be available to use.