You can't just put eggs under her and expect her to take them. You must wait until she is broody. A broody hen will sit on the nest all day, getting up only once or twice to eat and drink. To make sure she is broody, wait a couple days, and see if she stays on the nest. Then u can give her the eggs.
P.s. how old r the hens? In my experience, they don't become broody until almost a year after they start laying eggs