Try to run
git on the command line.
If it's already installed, it will show you how to use it.
Otherwise, install it using Homebrew:
brew install git
It is still necessary to set up your Git editor (enter
even if you installed for example VS Code during the installation of the editor).
You do that with this command:
git config --global core.editor nano
After that install and configure Git Credential Manager with command:
brew install --cask git-credential-manager
Now continue with the rest of setup at General Settings in Git install.