Show us what 'lsusb tells you.
If you can see the UART in the list, type this:
"lsusb -v -s xxx:yyy" where xxx:yyy is the Bus number and the Device number (not the hex ID numbers) then show us the result.
"lsusb" means 'LiSt USB devices", the '-v' means be verbose and '-s' list the descriptor and information table for the named device. As far as I know, all FTDI drivers have been built into the Linux kernel for several years now so you probably don't need any additional drivers.
Brian.