They are held onto the chassis with about eight bolts. I’ve pointed out three of them in the picture. It’s your job to find the rest. The rear skid plate will come off a little easier because it’s held in place only with bolts. The front skid plate is held on with bolts and two latches that keep it from falling on your face once all the bolts are removed.
After removal, you can throw the skid plates away or sell them on eBay because they won’t fit on the vehicle after the lift is installed. Besides, the new lift components look so good you wouldn’t want to cover them up with a skid plate.