In your Profile settings in your Account Information, you will see your login email. If you have other email addresses linked to your account, you can select a different email to be used as your login email. A confirmation email will be sent in order to ensure you wish to change the address.
If you do not have the email you want to change to link to your account, select Sender Addresses. From there, click "New" and add the address you want to add to your account. A confirmation email will be sent to this account. Once you confirm the address, you can return to your Profile settings and select the new email address. A confirmation email will be sent to ensure you want to change your login email. Confirm the email and your login email address will be changed.
Under Password, you are able to change your login password by entering your current password and then entering your new password twice.