Why manuals don't cover Library issues?

Hi,

I’m quite new to Arduino. When I bought my first board (it was Arduino Micro), I also download 3-4 manuals that cover basics of working with it. I read them all the way. I also read a lot of online materials, tutorials, watched videos, even ordered some hard copy books just to avoid any possibility that I might miss something important. I did a lot of examples, now I can do all sort of cool things with LEDs, buttons, various sensors, etc.

However, I always stumble whet it comes to installing custom libraries. This is still soo confusing for me. There are integrated libraries that I can call whenever I want. There are others that Arduino IDE will install, and I have no idea what this “installation” means. There are of course others that you have to find on internet, download manually, and then do something with them. If they are .zipped, you can “import .zip file”, and if they are not then you have to place them in some folder, I have no idea where. Well, there are so many things that beginners should know, and I have never seen a manual that covers this also. Is there any?

Please, point me where to look if I want to master library issues, including writing my own libraries.

have you looked here - https://www.arduino.cc/en/Guide/Libraries

DrugMile:
including writing my own libraries.

https://www.arduino.cc/en/Hacking/LibraryTutorial