Before you begin, check your supplies. You should have, at a minimum, the packages 1 (water purifier), 2 (eggs), and 3 (food.) If you are lacking any of these packages, do not start the process. Proceed down to the nearest toy store and pick up a full kit. Trust me, if you start now, without all of your required supplies, you will be disappointed.
Make sure the tank is clean, then add the water purifier. It is perfectly fine to use bottled water, distilled water, water-cooler water, etc. I wouldn't recommend Perrier or tap water, because of the extra minerals and fluoride, but it's your call, right? Please make sure you let the water warm up to room temperature before adding the eggs, regardless of how much time has passed.
Wait the required 24 to 36 hours (you can't go wrong waiting until the end of the 36 hours, but this could find you adding Sea Monkeys to the tank at 2:00 a.m., so do what you have to do.) You might see some Sea Monkeys in the water at this point. I have no idea why this is, other than to make some specious comments about time travel and Artemia Nyos, and this is supposed to be a serious page.
Stir the Sea Monkeys about and wait. You should see some little dots in the water, either white or black, but you will NOT see anything resembling Sea Monkeys at this point. But you have created INSTANT LIFE!
Now comes the fun part, ownership. Don't feed them for at least five days, and continue to feed them every five days thereafter. The water purifier and the egg packages contain enough food to get them through those first perilous days, so you will be okay. Ensure that you aerate the tank on a regular basis.
When you do feed them, always use the small end of the feeding spoon. I have found that using the large end, regardless of how large my Sea Monkeys are, leads to quite a messy tank. How do you know when to feed them? Look at your Sea Monkeys: You should be able to see a black stripe down the middle. That is their digestive tract. When that is clear, it means they need food. Feed them then. This should be about once per week, with the little spoon. What if you don't have a little spoon? Then get a McDonald's coffee stir spoon and fill about half of that. What if you don't have the growth food? Then don't start your Sea Monkey tank! Get yourself a package of food as soon as possible. You can order it from the Official Sea Monkey site or send away to Transcience. Do not feed them other foods...you will kill them. (Apparently there is something you can get from the pet store, but I have not tried it, thus I don't recommend it.
AERATION!!! This is the most important thing you can do to keep your Sea Monkeys alive. I cannot stress this enough! Ensure that you aerate the tank on a regular basis, a few times a day at first, then once a day after that. The aeration of the tank ensures that the little guys have enough oxygen in the tank. This is also why you don't want to add too much food to the tank; it sucks up oxygen and can kill the Sea Monkeys. How to aerate the tank? You can blow a straw in to the tank and do it that way (your breath contains about 16% oxygen coming out of your mouth, and that's enough for them.) You can also put a small plant in the tank -- it will contribute oxygen. Or you could swish the tank contents between a clean 12 ounce jar and the tank once per day -- they like it, don't worry about jostling them around.
Finally, it should take about one week before the Sea Monkeys look like Sea Monkeys. Don't worry if yours take longer -- there are variables in every procedure. They will be full grown in about 6 to 8 weeks, and they can start having babies at that point. Make sure you follow all of the directions above, and you will have some serious fun! Good luck!
I hope this is enough to get you started on Sea Monkey ownership. If you've read all of the instructions, and followed them, but you are still not having success with your Sea Monkeys, then please visit the Help! My Sea Monkeys Didn't Work! page on this site to submit your concerns to the Sea Monkey Lady. I'll do my best to figure out what went wrong and what you can do next. Please make sure you give me all the information requested, as it will make it easier to help!