Issuing the Pull Request
So you've made some changes in your local repository and propagated those changes to your fork on Github. You fully intend that your changes should make their way into the original project because you've worked hard and created some really nice changes. Now is the time for the pull request.
Open your fork in Github. At the top of the file list you should see a message similar to
"This branch is x commits ahead of WDM_git_tutorial:master"
However if master is being updated regularly you may see that it is x commits behind master.
Click the New Pull Request button or the Pull Request link.
This will take you to a new page where you can write details about the changes you've made. The title should be relevant but succint. Any additional details should be written in the description in order to sell why your changes should be merged into the project. You can add images and files to backup your changes.
Once the pull request has been opened it is up to the project maintainers to discuss and decide if they want your changes. They may request you make changes, usually to fix an issue they've noticed, because your content doesn't match their style guides or because the changes you've made don't fit with the general direction of the project.
If you are asked to make changes it's quite simple to do so. You can checkout your feature branch (if you've moved onto some other branch in the meantime).
$ git checkout my_feature_branch
You can then make changes and commit them. Once you push your changes to your fork the pull request upstream will automatically be updated and the project maintainers should continue reviewing the pull request.
Hopefully your changes will eventually be merged with the original project's master. Once this is done you may now delete the feature branch. This is optional but helps keep your repository clean. To delete the branch you can run the command
$ git branch -d my_feature_branch
You can also delete the branch on your fork using
$ git push origin -d my_feature_branch
For more information on the pull request workflow see below.
https://docs.godotengine.org/en/3.1/community/contributing/pr_workflow.html