Permits for Business advertising on cars.

Hi guys. I haven’t posted on here in a while. Used to deal with John Frank directly. Anyway, recently my wife and I have opened a Business English language school in Reforma. I was going to put some vinyl advertising on the car to promote the business but have since been told that I need a permit to do so. Has anyone had experience of this and if so can you let me know how much it costs and how to get the license. Any help would be greatly appreciated. ThankyouRitchie.