well if you have an xenium ice chip, once you successfully install it you will be able to flash a bios of your choice via FTP or using the webserver.
If not you will have to burn the bios & a dummy file... read up on a tutorial on how to create a bios cd (i think there is one on the TeamXodus website)
Once you have it on the harddrive or a DVD. Then you will start your xbox using the eject button and navigate to add new launch item or something of that sort and then pick flash and then find the file through the file structure. after that pick your color and you will be done. This is all assuming you have a ice chip with 2.01 or newer as your OS.
hint to make the box use this bios when ever you power set as default and then find in your Xenium Settins and turn instant boot on. I hope this is correct and i hope it helps.