Installing Prereleases on a Device
Install a prerelease on a device connected to your Mac if you want to prepare for new features.
Launch iTunes on your Mac.
For iOS and tvOS apps, connect a device to your Mac. For watchOS apps, connect an iPhone paired to an Apple Watch.
In the upper-left corner, select the device.
To upgrade to the latest operating system version, click the Restore button.
To install a prerelease, Option-click the Restore button, select the beta software restore image, and click Open.
The software restore image file has a
When installation is complete, activate the device and use iTunes to restore its contents.