Assuming you've asked for the email permission you'll have access to
the authenticated facebook user's email with:
$this->Connect->user('email');
Save into your users database however you see fit.
Example:
if($this->Connect->user('email') && !$this->User->field('email')){
$this->User->saveFiel
Presently i am using the Facebook Authentication Plugin by Webtechnik
but i have a problem i would like to store the email address of the
user into my database after the user has logged in. I have already set
the users details into a variable called facebook_user where I am
stuck now is how to save