First: Great that you're motivated to learn this stuff! When it comes to programmers I've worked with, usually the best ones are those who learned programming to do something for FOSS or wanted to create a thing themselves.

Second: If you're planning on university, an IT degree doesn't hurt. You'll learn a lot of stuff that -can- be useful. At the same time you don't need one.

Practically though, start learning a programming language that is relevant to one of the projects you care about. If you want to learn programming in general, start with Python for a very easy introduction to the basics. If you want to learn more about how computer work (you should), learn C. For learning programming, I recommend books instead of websites, especially if you learn a system level language like C.

Once you've learned a bit of programming - apply it! Go through the bugtracker of the software you use, and find a bug someone has already solved. Read what the bug was about, then read what changes were made and understand why that fixed the bug. The most important practical skills for a programmer are reading other people's code (especially for what you want to do) and debugging. Remember that the most common question a programmer asks is not "how do I do this" but "how does this work?" Another common one is: "WHY does this work?"

But you may also be able to contribute without programming. Many of the software you use requires people who understand how the operating system works to configure it, package the software, and help others like you to solve problems. All of this can be done without much understanding of programming if you spend some time to get familiar with the manual of your software and how the software interfaces with your operating system.

Good luck!