headphone help with mac os and discover DJ

i have been trying to figure out what would be the best way to get my headphones to play the cue song threw the headphones only....i know its a setup issue but cant seem to find a good result or a suggestion for an external sound card or audio interface that would suite my needs....
i have both an i mac and mac book with same issues. i am routing my laptop through headphone jack to my ion i DJ ipod mixer with the discover DJ hooked to my laptop via usb sound quality is fine just cant separate the headphones ....
any suggestions would be welcome
this is my first post so please forgive me if formatted weird
i have both an i mac and mac book with same issues. i am routing my laptop through headphone jack to my ion i DJ ipod mixer with the discover DJ hooked to my laptop via usb sound quality is fine just cant separate the headphones ....
any suggestions would be welcome
this is my first post so please forgive me if formatted weird