Apple officially released the first beta of iOS 12 for developers during the WWDC 2018 keynote. This version means that all officially registered developers can install the preview of iOS 12 right now .
However, you have the option to download the iOS 12 Beta 1 configuration profile file without having an Apple Developer account. Here is the procedure you must follow.
Step 1: Download the configuration profile directly from this link: ufile.io/ntrih with your iPhone or iPad using the Safari browser.
Step 2: Click the download button and select the type of device you are using if requested. You will then be redirected to the profile installation page. Choose “Install” at the top right of the screen.
Step 3: Once the installation is complete, your device will reboot automatically (If it does not restart automatically, restart it manually).
Once your iPhone or iPad has restarted, go to Settings> General> Software Update to download and install the iOS 12 beta 1 directly from your device.