how to learn libraries like sckit learn and PyTorch ?

so i learnd sckit learn a while ago but now i'm trying to do a project with it and i feel like i don't understand it like what to import and why and how to pick and all of this i don't just want to memories code that i'm gonna forget i open vid tutorial but i'm feeling like they all just implement the same thing like what if i wanna implement smth else how to pick and why

gonna start PyTorch so i don't need to fall in this same trap so how to start learning it ?