1.8i 16 Valve Cam Timing

[Guest Inch high]

Hi al, the engine in my wifes Xantia froze on Sunday night, thawed it out no probs but I suspect the cam belt may have slipped when she tried to start it, I've tried pegging the sprockets but to no avail, the crank will only turn a quarter turn around the locking peg point, do I need to set the camshafts up visually before locking the wheels and fitting the belt, if so could some kind soul talk me through it?

 

Thanks

Marc