(lovely photo from LovelyBicycle)
Get an old rubber inner tube. Cut two strips to wrap around the chainstays.These rubber strips must be wider than the area than the kickstand clamps. wrap the rubber strips around the tubes where you will attach the kickstand. secure them with electrical tape as tight as possible. Install the kickstand and tighten carefully but firmly as to not pinch the tubes too much. The rubber will provide enough insulation and protection for your frame and when you decide to take the kickstand off, there will be no residue when you remove the rubber strips because they're not glued to the frame.
Or you could just not worry about it. Some people uglify their bikes to keep them from getting stolen!
(photo from RivBike)
That's twine on the kickstand. Why? Well, it looks good. It also protects against something, I'm sure. So, it's useful. All you do is get some twine and wrap it, then tie it off and shellac it. Detailed instructions here, courtesy of the RivBike site.