If you want to start road racing motorcycles I would recommend first doing quite a number of track days. Become very comfortable on the race track. One of the advantages that we have nowadays is track days are plentiful and very affordable. There is no reason not to do a lot of them and to be very comfortable on the track before you think you are going to start racing. From there you need to figure out who your local race organization is. You do this by asking at local track day or asking at local tracks. Find out who they are. Some examples might be AFM, CCS, ARMA, AMA. So ask around and find out who your local organizations is and then from there you need to figure out how to get licensed by that organization. Some of them will have their own racer schools where you sign up and attend their classroom time and then go through a test and some on track experience with an instructor to make sure that your certified. Others will have you go to a track day where the same thing will happen but you will do it in a track day environment with instructors of that particular track day organizer.
Once you have done that you need to make sure that your gear and bike adhere to all of the race regulations. A lot of times this means safety wiring your motorcycle, replacing your coolant with water or water wire. Making sure that you have race tires. Proper oil and that everything setup has race body work and numbers on your motorcycle. So once you have got all that. All of your equipment and everything you can go an get certified. Go and get licensed and head out to the next race meet. Going there I would advise going on the forums and talking to some of the other racers asking all the questions about what to expect. Which races you should run when just getting started really any advice that your local racer can give you. Most of them are perfectly willing to talk to you and can offer you a lot more information than you can get online reading forums and sometimes they will help you out on your first race weekend out and then set your goals. Your first goal should be to just finish a race.