I would try them first with the point of the cleat pointing at your big toe or thereabouts, this will create a slight toe-out angle which is natural for most people, and should ensure your heel doesn't hit the cranks. I tried them pointing directly forwards once and my knees were aching within a couple of miles.
But trial and error after that to see what's most comfortable for you.
2011 Canyon XC 8.0 (Monza Race Red)
1996(?) dyna-tech titanium HT; pace RC-35's; Hope Ti Hubs etc etc
Bianchi Road Bike