To change your user name in Todo Cloud do the following:

-Log into your Todo Cloud account from your web browser
-Click settings (upper right corner)
-Click account (left menu)
-Move your cursor over user name and click edit when it appears
-Enter the email you would like to use


On you iOS devices Todo Cloud:
-Open Todo
-Open Settings
-Touch Account
-Touch Service
-Enter you new user name


On you iOS devices Todo:
-Open Todo
-Open Settings
-Touch Synchronization
-Enter you new user name