Forum:Extra Deck Extracting?

Can anyone tell me how to get cards out (other than synchros) of the extra deck? For example, there are only 3 copies of one card (i.e. Infernity Archfiend or Magical Stone Excavation) allowed in a deck. So can't I put three more in the extra deck? And if I do, how to I get them out of the extra deck? PLEASE HELP!!!