I commented on that issue with the status for each platform. For Windows, you can download an installer from Python Release Python 3.13.0b2 | Python.org. When you run the installer, you need to use the option to enable the free-threaded install.
If you want to install packages into a free-threaded venv that aren’t pure Python, you will most likely encounter some problems (as discussed in Windows installer, freethreading and building extension modules). Also, you need pip 24.1, which isn’t yet released (but you can upgrade to 24.1b1 with --pre).