looks like you are here in BC. If you are at a Spa they cover you insurance wise I believe. Ask them, especially if you are doing something you are unsure of. As we in Canada do relaxation massage, not medical massage ,in esthetics, often you will find Spas that provide hot rock treatments. I do long hour and a half ones. We have different regulation here. Spa therapists , not registered massage therapists do them all the time and so do we.
I was not taught in school but by a fellow Estie where I work. I do a lot of regular relaxation massage then use the rocks in place of my hands in some areas. There is a great youtube site called massage nerd you can use. If you are intuitive and good at massage then you should be good at hot rock massage.
Be careful with your hands and with the clients skin. I have a cool towel handy to place the rock in ( with tongs) to make sure it is not too hot. I also test in on my inner arm before I place it on the client. Just ask a lot of questions until you feel confident, make sure you are covered and maybe have a trial run with a friend or co-worker. Good luck!