I'm so late to this, but here's my 2cents worth.
Try and go and see an hypnotist for a single session and explain that you want to learn self-hypnosis. They will guide you into hypnosis which will make you familiar with the process. Perhaps they will, while you are in trance give you a "trigger" which can put you back in hypnosis when you do it on your own. It's not essential, though, it just makes it easier. This is how I began. (I then had some more hypnotherapy sessions but those were for specific problems) I've continued on my own since, first for self-therapy, then it evolved into the spiritual aspects.
Also, I recommend the website esdaileinstitute.com There are sound files there that start from the beginning. Of course there are others, if you google 'learn self-hypnosis'. There are a lot of YouTube channels, Michael Sealey's is a good one.