Details
To publish your repository to GitHub using GitHub Desktop, click the Publish repository button in the header.
In the dialog that appears, you can change the name of the remote repository, add a description, make the remote repo public or private, and make the repo part of an organization.
To finish, click the Publish Repository button in the dialog. You can check your account on GitHub to make sure everything was published correctly.
References
Push your repository to GitHub – GitHub Desktop Help