I have laying age hens that are not yet laying. What can I do?

Don't panic yet. You may just have a breed that takes longer to mature than regular chickens. If your hens are older than 10 months then you will need to address both living and nutritional factors.
First, make sure the hens have at least 14 hours of light provided, either daylight or artificial. Less than 10 hours per day will retard laying to near zero. If possible allow the birds to free range during daylight hours, at least in an outdoor pen.
Supply a good commercial laying mash or pellet for a few weeks if they only get scraps and forage now. Make sure the hens have plenty of fresh water available 24 hours per day, water deficient birds will not produce eggs.
Provide laying boxes that are quiet and dark. somewhere the hens can get away from the flock to rest and concentrate on the job at hand.
Try using a water soluble Tonic available from all feed and grain supply stores to boost vitamins, egg production takes a great deal of energy and poorly fed birds will use all theirs just staying away from starvation.

Also it is roughly based around how much light they are getting, how much food they are receiving, try putting a rubber egg in their nesting boxes to get them broody to lay.