I highly recommend Martha Peterson’s introductory video (Pain Relief Through Movement) or her book (Move Without Pain) to learn more. https://essentialsomatics.com/
There are also a number of free videos online to teach you fundamentals. Here are a few instructors on youtube:
These movements may not look like much, but try them and notice the changes that result!
Although you can definitely learn with the above resources (that’s what I did for several years), group classes or one-on-one sessions will give you the opportunity to receive feedback, so that you are more aware of muscles that you don’t consciously realize you are tensing. This will result in faster progress, and less frustration.