Open Source Roadmap: How to contribute
You can do a lot from the GitHub UI.
Fork the repository
At the top right of the repository page there is a fork button. Click that to make a copy of the repository in your own GitHub account.
Now you have a copy of the repository in your own GitHub account, you need to make a new branch from the main branch. Click on the branch button and type in a new branch name. This will create a new branch from the main branch.
Find the file you want to make changes to and edit the file. Then commit the changes to your new branch. You can add multiple commits to this branch if required.
Create a pull request from your new branch in your fork to the main branch in the original repo (aka upstream). You might need to click on: compare across forks.
If you receive feedback where you need to make changes, you can add additional commits to your branch in your fork, GitHub automatically add them to your open pull request.