add an activation field too into your table, then write some kind of an encrypted string.
if you google on SHA1() you will find lots of useful random code generator.
If you ready with this code ( $hash ), lets make a link to an activations.php , and send with an email:
$to = $_POST["email"];
$title = "Registration ..."; //it will the emails title
$message= "You have registered into [page]: \r";
$message.= "Please click here to activate Your account:\r";
$message.= "http://www.mysite.com/program_folder/my_users_members_activate.php?activate=$hash \r";
if(mail( $to, $title, $message ))
print "Activation email has sent!<br/ >";
After make an activate.php where you select the activation code from the table, and if its in, make a form to confirm the user's password. If its matches, lets update the table to make the user enabled now!
If you still need more examples, just ask 🙂