Hi Cathy, one of our hometalkers posed a similar question a while back. She painted her kitchen cupboards and wasn't to happy with the results. She used "Awesome" spray that she found at the Dollar Store and spray it on and then wiped it off with steel wool. Here's the actual link to the post if you want to read through all the comments and suggestions - http://www.hometalk.com/2640675/q-stripping-off-a-lot-of-chalk-paint
If it hasn't been sealed (and especially if it's fresh) you can rub it off with a wet towel.
First you will need to use mineral spirits to remove any wax. Then you can paint over the chalk paint.