See -> https://github.com/vanvught/h3dmx512-zip
The kernel.img file must be copied to a SD card (FAT partition) along with the Raspberry Pi firmware files:
bootcode.bin
fixup_cd.dat
fixup.dat
start_cd.elf
start.elf
The Raspberry Pi firmware files can be downloaded from https://github.com/raspberrypi/firmware/tree/master/boot
When using the HDMI 7" 800x480 Display, then you also need to add a config.txt file with the following :
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0
Reference : https://learn.adafruit.com/adafruit-5-800x480-tft-hdmi-monitor-touchscreen-backpack/raspberry-pi-config