Brine Shrimp are very easy to hatch, a bit harder to keep long-term, though its frequently done as well. Did you buy them in a labelled package/bottle? It will tell you the salt ratio to make up for the hatching mix. Otherwise, you need to get some salt mix (don't use tablesalt - it usually has iodine in it) from a aquarium shop and make up a basic sea salt mix. You need to keep the container aerated and in constant movement so the eggs and hatchlings dont settle on the bottom - an airstone & pump is all you need for this. You then put them in a dark, warm place to hatch, which they will do with-in 24-48hrs, depending on the temperature. Once they have hatched, you need to separate the hatchlings (napauli) from the left over egg casings - this is very important if you plan to feed them to fish fry or seahorses because the shell casings can be eaten instead of the napauli and cause the fry or seahorses to starve. The napauli will go through a series of moults as they grow bigger and these left overs will need to be siphoned out of the water as well or the water will become fouled and kill your shrimp. If you intend to raise the shrimp to adult stage and keep breeding them, they need to be fed. "Green water" is best because you can make it yourself easily enough but you can purchase and use liquid fry (baby fish) food. Again, you have to make sure the water doesn't foul so only feed a few millilitres at a time. There are hatchery kits you can buy from pet supply shops that are designed to make the collection of the shrimp and siphoning of the left overs easier. Haven't used one yet but plan to get one so I can feed my marine fish every day. Good luck
I used this online video when I first tried - have been very successful.
http/www.youtube.com/watch?v=Y8sNx9zTOnQ