If you would like to change the email address that you use to access the system, all you have to do is go to My Account > User Administration.

This will allow you to amend user details so whether it is yourself or one of the other users in the system you can change the log in details if you are the Master user of the account. 

Then all you have to do is press the "Edit this User" and this will allow you to edit the log in details and once you are happy press "Save".