AudioMoth Labs is where we share experimental software and firmware. This includes prototypes for upcoming functionality and tools which can help maximise the utility you get out of AudioMoth devices.
For firmware, each Labs page will state which hardware versions it will be compatible with. If you have a device which is compatible, then installing the alternate firmware is as easy as downloading the binary file and flashing your device with the AudioMoth Flash App by selecting Use Local File and navigating to the firmware file.
Note that you should not select Overwrite Bootloader unless explicity asked to do so in the instructions associated with the specific firmware you are attempting to apply to your device.