You can only change the email account registered on Deskree if you signed up for Deskree using an email and a password. If you authenticated using OAUTH, you will not be able to change your email or password.
If you registered for Deskree using an email and not using OAUTH, click on the small arrow beside your profile avatar:
click on account settings:
Here you will see the option to edit your email:
To change your email, you will need to enter in your new email address as well as your current password:
When you are finished, click "Save".