Contributing to an open source or entreprise repository is mandatory to all developers how start coding.
The first thing you should do after creating a GitHub account, is to make sure you secured it with N2F authentication (GitHub Mobile Application/SMS/..) Make sure you have an SSH key, this is important for you and not only on GitHub. To create a SSH key, just follow this link
It's not a war of best OS, with Docker, all systems are same if you a are familiar with it, ignoring garbages files like DS_Store and showing hidden files is very important, so, don't push them!
You should know that in GitHub, developers are using Git to create branches, tags and Pull Requests. You should understand how to deal with them.