If not, you can shut down your Mac, reboot it, and then retry the installation process. On the occasion that you can't shut down your Mac, press and hold the power button for 10 seconds to perform a force shutdown.
If not, you can shut down your Mac, reboot it, and then retry the installation process. On the occasion that you can't shut down your Mac, press and hold the power button for 10 seconds to perform a force shutdown.