Imagine the name of the FTP server is FTPSERVER.pkg and you want to be able to install it to your ps3 well this is how you have to do it...
Go onto your computer get FTPSERVER.pkg (download it) then put it on your usb root NOT IN YOUR PS3 FOLDER!
The root of your usb is the usb itself so as soon as you open your usb theres the root put the FTPSERVER.pkg on it then blug into ps3 and go to install pakage files and install