Associating milestones with issues and pull requests
You can associate similar issues and pull requests with a milestone to better track their progress.
On GitHub, navigate to the main page of the repository.
Under your repository name, click Issues or Pull requests.
Select the checkbox next to the items you want associated with a milestone.
In the upper-right corner, click Milestone, then start typing the name of an existing milestone. Click the milestone's name to associate it with the item.
As you're working on issues and pull requests, you can track the progress of your milestone.