Changing Email Adresses:
You may change the email address that you have on your account by hitting the "Update Profile" button after logging in on the left hand side of the screen, and then "change password/email" located at the top of the next screen.  This will only change the address that email blasts are sent to, NOT your registration form.
 
Adding additional email addresses for blast emails from league:
You must register a separate account in the registration system for each email address you would like to receive blast emails from the league.  Hit the "Create Account" button on the righthand side of the page under Short Cuts to register all new email addresses.