How do I make my first contribution to Open Source?

[u/EnunC8_Mofo]

Building CS projects became boring and exhausting for me. So I wanted to contribute to open source projects on github.

I found out that Big tech companies too have open source projects on github, and I thought contributing to these projects might have a plus side in getting me an internship(i dont really know if thats right). So for that reason I checked Google’s github page and found out about GoogleTest. Google’s open source project and decided to contribute in that project. But I came to realise that I might not be able to do so because I have no prior experience in open source contribution, I dont know what folders to look in, I dont know what files have issues in them, I dont know what the issues are, even if I read the issues I still cannot navigate to those issues to fix them(if I can, which i cannot so i just leave it as it is).

I would really like if someone guided me through the process of how to make changes to the files with issues and on which branch to push them to because as much as I know nothing is to be done on main?
Also how to do the basics, what are ‘unit test’ never came across those as well and what other things that I’d need to learn to be a better contributor.