According to http://android.processing.org/install.html
In order to do this, first download the AndroidMode-xyz.zip file for the desired release or pre-release from the releases section in the GitHub repo of the Android Mode. Uncompress the zip file and then move the AndroidMode folder into the modes folder inside inside the sketchbook folder.
This is very confusing for me. I have downloaded the Android Mode 0258 (https://github.com/processing/processing-android/releases) and tried to copy the main folder (renamed to "AndroidMode") to "modes" folder in Processing folder and it doesn't work.
Or maybe I understood this instruction wrongly? What does it mean " inside the sketchbook folder"?