There are 3 places where you need to update your email address:

1) You can create new FROM field under My Account >> Set My FROM fields.
You can set different FROM field for each campaign under Campaigns >>
 Settings >> General Settings >> FROM: field

2) The email address for delivering subscription notifications
can be changed under Campaigns >>  Settings >> General  Settings>>
Subscription Reports.

3) The third place to update your email address would be under
My Account >> Edit Account Details.