I have often encountered this problem. There is a library that promises to do something that I need, would really be good to have. But there is almost no documentation on it. I can't even install the library in some cases.
I just had this problem with the Autotune PID library. They guy has literally no documentation on how to actually use the library. There is one blog post on some high level details of how it works, and that is it. There might be some example code, but I couldn't install it from the zip file so I can't even know. It just says there is no valid library. It's from 2012, maybe there's the problem. But the tutorials are for it, there are no more recent tutorials. I suppose people with better programming skills can jump in and use it without, but this seems to be really common.
It is baffling and infuriating that people do good work and spend a lot of time making these libraries and stuff, but then they don't bother to produce a short document that tells you something about how to use it?? Thus it ends up being useless, at least to some of us. I had this problem with the TMCstepper library, too. Why do so much work writing code and then not document it?
How do you go about using this code that's not very well documented? Why does this keep happening?
I had to give up. For some reason it and the arduino pid library are not in the arduino library system accessible through the ide, anyway, which is also baffling. I tried to get another autotune one working, sTune, but wasn't successful. I never found a solution, I have to keep trying tomorrow.