Crackle nails are fun and easy. You have to buy crackle nail polish. It can get pricey so look around for a good deal. First I painted my nails one solid color. I let my nails dry a little bit. I don't worry if they're not all the way dry.
Now apply the crackle polish generously. I don't like to do it thin but that's a personal preference.
Crackle dries very quick so move quickly when you're painting your nails. And just like that you have crackle nails.