To change your email address, log into the My Account section and scroll until you reach "Account Settings". There, select the "Edit" button that appears next to your email address.
Enter your new email address in the field, and click "Update".
To change your password, log into the My Account section and scroll until you reach "Account Settings". There, select the "change password" button that appears next to your password. 
Enter your new password in the field, and click "Update".