Advanced Tip: The best way to download and install iOS 12
Note: The following tip is for those who are registered Apple Developer's. This tip may not work if you do not have a registered developer's account.
Registered Apple developers already know about Apple's Developer's web site and how to get the necessary files to download and install developer betas of iOS 12 via iTunes.
What you may not know is - there is a much easier way to download and install the current beta of iOS 12 - and you can do it all from the iOS device.
Here's how:
1. Navigate to the Apple Developer's web site on the iOS device.
2. Login with your developer's username and password.
3. At the menu on the left, select DOWNLOADS.
4. Scroll down to the iOS 12 beta image section.
5. Select the iOS Beta image file and download it right on to the device.
6. Tap YES when asked if you want to install this profile.
7. The profile will then be installed.
8. Reset the iOS device.
9. Once at the main screen, select SETTINGS > GENERAL > SOFTWARE UPDATE.
10. The update panel should show the newest beta of iOS 12.
11. That's it.