I asked my AI tech.  I watched some online videos and took a day course at a local dairy put on by the AI company.  They brought a repo tract, but a guy could get one from a butcher (old cow) to see to.  Biggest help I had was doing a couple alongside my AI tech.  If I had difficulty he took over and explained what was going on (vaginal fold, wrong spot, etc.)  Glad I learned since few AI techs in the area now, and I really did not get comfortable until I had bred a hundred head.