How to contribute to someone else's repository?

Question

I have a friend who has a repository in his GitHub account. I want to contribute (pull/push) to the master branch (the only branch) on that repo directly.

How would

Answer 1

The above answers are missing details.

Github's docs directly answer this question and clearly say the original repo should be added as another remote so the PR can be pushed, i.e.

git remote add upstream 

Your own fork on Github can now be pushed to as "origin" (or whatever you labelled it), but the original repo can be pushed to as "upstream" (or whatever label to differentiate it from your fork).