Generally, it will take 21 days for eggs to hatch
after they are either incubated or a hen sits on them.
Is the hen now laying on the eggs (brooding)? You also need to make sure the eggs are fertile and can do that through candling.
eLengo also offers an online course in poultry farming if you are interested in further education.
Find out more information here.
@nedward may also have some insights for you!