The preview is supported on the following phones and tablets: If you simply can't wait for the Android beta, flashing the new version of Android is going to be your best bet.
If you are following this guide and using a Windows machine, you will not need to use the "./" seen in the guide.
That means that if you have one of the eligible devices, you can simply visit the Android Beta portal and opt-in to the beta, which will then prompt Google to send your phone or tablet an over-the-air update.
If you're already in the public beta, you will receive an over-the-air update to the final version of Android 8.1 Oreo shortly.
When it is done flashing the bootloader you should reboot back into the bootloader as to make sure everything is still working correctly.
Finally, it's time to flash the actual system image to your phone or tablet.(Or if you know that you can drag a file into a terminal window to copy the path, just do that.) To begin, make sure you are still in the bootloader menu on your device and double check that your bootloader is in fact unlocked.