Sounds like you are in over your head. As the Admin told you, you need to add a password field to the form.
<tr><td><label class="">User Password</label></td><td><input type="password" name="userpass" id="userpass" width="200" value="<?php echo $memberedit->password;?>" onblur="checkPass(this.value)"></td></tr>
You should actually have two fields...one for the password and another to confirm that they typed the password in correctly.
You are then going to need to write a javascript function checkPass() to validate the password for acceptable length, chars etc.
You will need to fill in the password form value from the database just as the code does with the other field values. You will need to add additional sql to update the database with the password field value. It looks like the admin gets sent an email after an update, so depending if he wants to know the password used, you will have to add this to the email form as well.