mahoteacher,
1. Start recovery mode (Hold down [Enter] key during restart), Choose Export over USB):
Code:
I -> Initialize partitions
O -> Format Userstore
E -> Export over USB
U -> Update Kernel + Rootfs
Q -> Quit and Reboot
Warning, Do not choose O, I options, you will damage your Kindle
2. Connect to computer
3. Unpack Duokan system files into Kindle root folder (As usual Duokan install, except copying *.bin files).
4. Restart Kindle