I'm not going to lie...cartwheeling is hard. It's one of those moves that is hard to teach, hard to learn, and requires a lot of technique. It's one of those moves that you have to try and try and try until you get the "Feel" of throwing an end or two. Some people learn in flatwater first, where as others do better starting out in a hole. I, myself, learned in flatwater and it took me a little while before I could even double pump (initiate the bow and stern in flatwater). In other words, don't be discouraged. Some people get it quickly and for others it takes more time. In the process, you'll learn all about edge control, leading with head, and incorporating your core muscles into the move. Overall, you'll be a better paddler.
Here's a quick little video that breaks down how to cartwheel in a hole. Let me just say the new Project X is pretty good at cartwheeling...
In my next how-to post, I will go over a few flatwater drills that help improve edge control and get you cartwheeling!