exit airport, left at the roundabout heading towards the city, take the sliproad off to the left at the kinsale road roundabout heading west. (I'd stop for grub at the Mills Inn in Ballyvourney myself) Follow the road straight ahead past ballincollig onwards to macroom, and continue through killarney. At Killarney follow the signs to Tralee. At Talee follow signs for Dingle.
I think there's another route through Killarney also towards Dingle, but never done it so can't be sure
hope that helps.
Allow 3 hours or so plus eating time