If you are committed, it is worth reading through all of learncpp.com (excluding chp. 0).
I know it is a lot of reading, but it will teach you everything you need to use PROS effectively.
However, you don’t need it. PROS is just C/C++ with a similar API as all the other solutions. There is nothing particularly complicated with it. It is only as complicated as the user makes it.
However, PROS allows for more complex programs, and has a lot more features and libraries you can use. That is why it is good to know your way around C++, so you can properly use PROS the way it is meant to be used.
PROS is not great for beginners simply because it is more open and vast, so programmers need to know more to be able to navigate around and understand what is going on.
You can make very similar code as VCS if you choose, its just that PROS prompts you to become a better programmer by learning how to refactor and abstract your code, and exposing you to more C/C++ lingo and functionality than you would otherwise encounter in VCS.
If you know how to make things more neat, use header files, understand C++ beyond copy/paste, and know how to properly structure C/C++ programs, you will have a much better experience with using PROS.
Edit: learncpp.com chapter 1-8 are the most important, though if I had to pick the best, 2, 4, 6, and 7 are the most important.