Mastering yourself is difficult and may even be dangerous! To begin with, you need to answer yourself the question why you need it, define goals and objectives for yourself and see how yoga answers them. Once decided, it will be easier to find the instructor or school that suits you, from whom you can get the basic basics and safety techniques that will be adapted to your goals and individual characteristics, and then continue to practice on your own, receiving periodic feedback from the teacher. Ultimately, yoga must become an individual practice! This is when yoga is seen as a technique for achieving practical results.
You can start doing yoga, for example, finding a good book, reading articles, trying to do asanas. Carefully. Then there will be a need to consult with someone, ask questions, discuss practice. Fortunately, now there is a wide selection of different yoga classes, studios, schools. Come and see. What you need from the teacher to begin with is to explain the safety technique to you, correct it if you are doing something clearly wrong. Your home independent practice and sincere interest are more important than an admission to a yoga studio or an enrollment in a group with a teacher. But you should not completely isolate yourself, from time to time it is very useful to get some kind of independent examination of your own practice - whether you are moving there. In general, yes, for successful practice, some reference point is needed in the form of an experienced yoga teacher, all sorts of ancient texts on yoga speak about this, and, as it were, common sense.