Here's a website with some great information about what's required to become a CNA instructor. You'll have to look into your specific state requirements to see if anything more is required of you. According to this link, all states require that CNA instructors hold an RN license and have at least a couple of years of experience. Some require experience specifically in geriatric nursing. Then you'll need to complete an approved training course to learn how to be an instructor.
As far as how much you will be paid- that will depend entirely on your location, where you are employed (employed by a community college, hospital, nursing home, trade school, etc.) and how many students you are teaching per class.