[b_emery]

Get a few lower division (first few years of undergraduate) textbooks and start reading. Work the problems at the end of each chapter. Ideally find books with solutions or at least the answers, so you can work these problems until you understand them. When you get stuck, find someone you can go to, or consult other texts which often give a slightly different, often very helpful, point of view. Also ideally, you would have access to a library so that you can get a few texts.

Personally, I believe the best way to learn anything hard is by enrolling in a course. Having some kind of commitment, and looming consequence, forces you to work through the inevitable tough patches. You can also get a lot of help from classmates, and or learn a lot from helping classmates. They can also be a social support network.

Regarding your comment in the thread, you might want to make sure that it is physics that you want to learn. Physics is more the study of how things are, the nature of reality, rather than 'why' reality is a certain way. There are not many satisfying answers to questions like "why does light have wave and particle properties", but this might be semantics. Physics explains a lot about what we observe. I get a lot of pleasure out of knowing why the sky is blue, how a rainbow is formed, etc. My BS in Physics is an excellent foundation for what I do now, which is radar oceanography.