Hens 'sitting on eggs' for the purpose of hatching takes 21 days (and that is around the clock!)... after she gets enough eggs gathered to hatch them she quits laying eggs at that point and commences to the sitting tight. This is great except that many hens are happy to just sit in a nest an hour or two a day, lay their egg and walk away. That is normal behavior. Broody happens much less often!
Hens 'going broody' is based on hormones and genetics. Some hens 'go broody' frequently, some may never get 'in the mood'. And until a hen decides for herself there isn't a whole lot you can do except wait or use an incubator.
You can figure a hen is broody when she takes up near constant residence in a nest, only coming out for quick potty, food and dusting breaks once or twice a day, she will often 'talk' excessively while she is out on these breaks also and may strenuously object to humans or other chickens bothering her while on the nest. Once a hen is broody she will hatch out any egg you give her, she doesn't care if it is hers or someone elses, it can even belong to a duck, she probably won't care... she is just programmed to sit by that point!
If you want to hatch out eggs by using hens instead of incubators then check out the breeds tendancies, because some 'go broody' a lot and some breeds very rarely will ever get that way anymore (many have had the trait bred out of them because people didn't like the drop in production that went along with the broodiness, because broodies quit laying when they start sitting and may not lay again for a 2 or 3 months when they are done being 'mommy' for a while)
So to answer your question... if one of your hens was broody she would hatch out any fertile eggs, but if none are broody you are out of luck for that.
Check out this recent article on the subject...
https://www.backyardchickens.com/a/encouraging-or-discouraging-broodiness-in-your-hens
Here is a long but informative thread on the subject of broody hens
https://www.backyardchickens.com/t/...ody-hen-hatch-a-long-and-informational-thread
and another thread with broody question
https://www.backyardchickens.com/t/621910/how-can-i-make-my-hen-go-broody
But you can't make her go broody, though there are things you can do to encourage it. Once you have a broody, though, you can stick whatever you like under her and, if she's good at it, she'll hatch it. 
