Step 2: Install the bootloader
In order to make your iPod load and execute the Rockbox firmware you have just installed, you will need to install the Rockbox bootloader. Unless bugs are found in the bootloader code, or significant new feature are added, you will only have to perform this step once.
These steps use the ipodpatcher tool. Source code is available in the Rockbox SVN (see UsingSVN).
thats exactly what it says and the Rockbox SVN and UsingSVN are links...