Sanding or paint stripper.
Hello Nancy: Here are a couple of sites that may help:
Depending on what it is on there are different directions:
If you're painting over it, you don't really need to remove it. But, everything seems to say that sanding is the best way to remove it.
Hi! Blue Bear soy gel paint stripper is great at removing chalk paint and is also non-toxic, can be used indoors!
You can sand it off or use stripper and a plastic scraper. I like citri-strip the best. Wait until it bubbles and scrape the paint off.