Godspupil I update using the ASIAIR plus update button, how do I use the link above?
Apple TestFlight is for use with Beta software. You need to first install TestFlight from the Apple App Store. If you are uncomfortable with installing unstable and undocumented programs, do not use TestFlight.
You then go to the Apple web site above and tap on the ASIAIR icon on that page to allow yourself to be registered as a Guinea Pig for the ASIAIR app and firmware. After that first time, you can just launch TestFlight in the future, and ASIAIR will be one of the test programs you can download.
Once you launch the ASIAIR Beta app, whose payload includes the Beta firmware, you will be asked to Update the firmware. Doing so will replace your existing firmware with the Beta firmware. At that point, the Raspberry Pi is running the Beta firmware, and your tablet is running the Beta app.
If you are using the third generation ASIAIR, you need to "reset" the firmware if you want to revert to the old stable version. If you are using the first two generations of ASIAIR, be sure to first archive the existing microSD card since that is the easiest way to revert firmware.