second ethernet card

Hi I been trying to set up an second ethernet card to just talk to my other machine it doesnt need to go out to the net just so i can transfer file from one machine to the other locally but it seems when i put the card in it doesnt see it and i try to manually set it up but then i mess up my dhcp to my isp so if someone could explian on how to do this maybe we can get this to go thanks in advance Bob