You can easily update your email address from your profile. Navigate to your profile by clicking the on your name in the upper right corner and choosing 'Account Settings' from the drop down menu.
Find the 'Email' card at the top of the Account Settings tab. Click 'Edit' at the bottom of this card. Enter your preferred email and current password and click 'Update'.
If your organization does now allow you to change your primary email address, please contact your System Administrator.