When you want to grow your skills, there are a lot of different things that you can do in order to acquire what you need. You can go to a school environment, you can take up a sort of apprenticeship under a seasoned mentor, or you can mostly go it alone. If you have access to a school or a mentor, these are generally your best bets. But in some cases, your best option (and often your only option) is going to be to train yourself in whatever you want to become more proficient at. While this does tend to be a harder tow to hoe, in the end you may end up learning more than you ever thought possible.
After all, consider that the first people who ever learned much of what our species knows today (often the first people who ever taught it to anyone else) had to first learn it themselves through observation. If they were the first people to learn it, how else could they have, but through what they noticed with their own eyes and interpreted with their own minds?
But how do you plan to train yourself in anything? In this day and age, you have an unprecedented number of different options available to you, when it comes to learning something on your own. You can look up untold amounts of information on the Internet, check out books from the library, and even observe people doing what you want to learn. While the quality of the learning is going to be lower to start with (since you will literally need to learn all of it without guidance, making your own mistakes), the end results will ultimately teach you better.