macOS is available by default on Apple computer. If you run a different operating system, please refer to the other section of the documentation.
To run Home Assistant on macOS you need to install Python first. Download Python from https://www.python.org/downloads/mac-osx/ and follow the instructions of the installer.
Open a terminal and install Home Assistant.
$ pip3 install homeassistant
Check this video for the installation on macOS.