...
From your unity project folder:
npm init
npm install --save git+ssh://git@github.com:shadowmint/TEMPLATE.git --no-progress
echo Assets/pkg-all >> .gitignore
echo Assets/pkg-all.meta >> .gitignore
To avoid typing the password in every time, consider using ssh-add.
The package and all its dependencies will be installed in your Assets/pkg-all folder.