When you receive the package you can start immediately. Put the content in a bowl with about one liter of water, about 3 cm water level.  Use water from a well cycled tank or rain water. Keep the bowl or container covered as the eggs are light sensitive. When the eggs get dark (eyeing up) they will hatch within a few days. Now you can uncover the container and slowly start feeding. For the first days they can be fed with infusoria (you get them with your order) , after a few days they are ready to take live brine shrimp along with powder dry food. After 2 weeks move them to a well cycled tank as they grow faster in a larger tank. Keep them in a tank of about 10 litres until they are 2 cm in length then you should move them to their final fish tank.