To use this project template you will need to have Unity 2020.1.8f1 or later installed.
You can use Sourcetree https://www.sourcetreeapp.com/ or GitHub Desktop. https://desktop.github.com/
If you are new to Git I'd recommend using GitHub Desktop as it's the most simple.
If you are using one of the clients above, a popup will appear when you clone the repository.
It's important that you do this before opening the project in unity for the first time, as there are files generated according to the project folder name.
(if using a newer version of Unity a warning about the mismatch between the last saved project version and the editor will appear. ItThis is fine. Click confirm to upgrade the project to your newer version)