1. You have to have sufficient abdominal muscles.
2. You have to be lean enough to allow those muscles to pop and show through your skin. This is the hardest part. You can do all the crunches you want, but if your body fat levels are too high, you may never see those abs. This requires strict and long-term adherence to a proper diet.
If they were easy to attain, then everyone would have them.
If you can nail both of those steps, then you can have abs too. 🙂