Ask HN: I want to contribute to OSS projects, what resources should I read?

Specifically, there is a bug in Icinga2 (an open source monitoring app written in C++) to do with clustering which I'd like to at least help debug, if not resolve and help fix.

I grew up learning PHP and became a sysadmin so I've picked up, to a reasonable degree, a few scripting languages: Perl, Python and BASH (Python can be used for 'proper programming' but I just used it for simple data grinding). I'm used to writing scripts in vi, then in another terminal executing them, rinse and repeat until it works, put it under source control, done. Writing PHP/Laravel is similar - I never need to compile anything, just set the environment up, write it and refresh it until you get it right. I'm a bit of a self-taught hack-learner, so I've never done tests with deployments or so on (sorry).

I've downloaded GitHub projects (like Icinga2) and ran simple configure/make commands, but I'd like to be able to better understand what's going on. Ideally I'd like to pull the source for this project (Icinga2) down, learn how to compile and re-deploy it to a test setup easily, so I can add additional debug output at least. I know it's more work than scripting but it's something I'd love to learn as I could contribute to a few OSS projects, I learned C at university and did some C++, but it wasn't real-world use, but generally I enjoy problem solving so it'll be fun.

Looking for any blogs or resources around contributing to OSS, how to write tests, local test/debug setup for a C++ project like Icinga2, and anything else that might be relevant - any advice appreciated.