Congrats on the hatchlings!
Randy is right, its really best to have someone show you how to do it if you have not done it before.
Also, you can have that person teach you how to "pop" them as well. Many of us pop first and if they don't pop male, we probe to make sure its a female. I always double check like this so people don't end up with 2 males!
Kathy love has some videos on her website (link below) that show you how its done, but I still think you should have someone show you in person.
http://www.corn-utopia.com/Corn Utopia on the Web/- Sexing corn snakes - intro to vid clips.htm
Good luck.
Dave
DNS Reptiles