This is not the best way to add a local project to github. It is just a way that works using Visual Studio and GitHub Desktop with a small manual intervention.
A shorter path is possible by letting GitHub Desktop create the repository.
Using Visual Studio right click on the solution in Solution Explorer and select Add Solution to Source Control. This is equivalent to:
git init, creating .gitattributes and .gitignore files and
git add ..
Create a new repository on GitHub, add a description and do not select Initialize this repository with a README.
Open Git Bash and go to the solution directory.
Copy the https url from the repository creation page.
git remote add origin https://github.com/gabrieleteotino/CommandLineExperiments.git
Verify the new remote
git remote -v
From GitHub Desktop select Add a local repository browse to the solution folder and select Add Repository.
After a few seconds the repository is ready to be pushed. Click on Publish branch.