How to make the installation USB:
See Imaging Instructions for CFE and U-Boot.
How to boot to the installer:
See Booting Instructions for X1000 and Booting Instructions for X5000.
How to install Fienix on the same drive as AmigaOS (or other Linux):
Fienix Installer for CFE and U-Boot does not include functionality to install Fienix onto multi-partition drives at this time. You will need to manually set up the partitions and copy the Fienix Live Image.
