I cloned typeshed but I can't figure out how to tell mypy to use the type hints it contains, I see no option in mypy --help. The mypy repo does contain reference to the typeshed repo, but pip installing it doesn't not download it.
Mypy comes bundled with typeshed by default, so you shouldn't need to do anything -- simply doing
pip install mypy-lang will install it correctly.
Note that typeshed is not a Python module, so it isn't possible to import it or otherwise access it from a Python program unless you literally look at the location in the filesystem the stubs are stored.