Adding a Custom Field to Registration Page?

[BobbyT]

Hello guys,

I would like to add a Custom field into my Registration page for my users to enter their 'Identification Number' that was given to them beforehand (I am running a group site). Afterwhich, an Administrator would verify their 'Identification Number', and approve their registration into the site. How do I go about doing this?

PS: Sorry if this is in the wrong Section. If the moderators wouldn't mind helping me move it? (if it's the wrong section).

Cheers!
Bobby