It is a long time since I set up any BTMail email addresses but from memory you do not see the "family and friends" section until you have actually set up an additional email account and "gifted" it to another.
This then moves the email address from being one of your email accounts that you have all the functions to fully manage it ie change password and delete , to the "family and friends" section where you can no longer access it or manage it,(without knowing the password) because the recipient of the email account now becomes the owner and manager.ie they can change the password.
All you can do is remove the email account from your BT Broadband account. ie delete it.
