That would really depend on when you want them to come on. The LED's won't draw much at all so i wouldn't even bother with a relay.
If you want them on with the parking lights, you can wire them up to the parking lamp (note that the lamps for our turn signals have two elements). You can find the one for the parking lamp by turning the parking lights on and using a multimeter. Someone else on this forum may already know the wire color/location.
If you want them on independent of everything else, you'll need a new switch in the cab.