Connect your Forerunner 235 to your computer using the USB cable.
My change to GARMIN's instructions:
Copy the entire GARMIN Folder to a location on your computer as a backup then delete everything inside the /GARMIN folder (Don't worry the Update will re-populate all these files with the same time date.) Delete the ERR_LOG.txt in the root folder.
Download and unzip Forerunner235Beta.zip. Place the GUPDATE.GCD file in the \GARMIN folder of your device's internal storage drive.
Disconnect your device from the computer, approve the update on the watch, and wait for the update to finish.
The suffer score requires 4.30 I suppose ? I'm still on 4.20 but I'm staying there as I'm worried my custom HR fields might get wiped out...are you still on 4.10 ?