There are multiple ways to create the plays in Playground application. Lets explore the option for getting the details from a public repository. Users can upload their solutions directly from bit based source control(Github/Bitbucket) to Playground. This options requires a public url of your repo to setup a play so this means your repository should be public. The user need to make sure that the Repo follows the same structure as that or Salesforce.
Click on the Add Play button which is location at the top right of screen.
This will open a popup with selection for importing method. Lets choose Public Repo and enter the git url of the repository.
Enter a valid and meaningful name for the play and click on Continue.