Need a 2nd dedicated USB port for Mega2560 for Midi Controller

Projects General Guidance
6

This is the ftdi I have

http://www.ebay.com/itm/GeTech-USB-serial-FT232RL-converter-Light-Arduino-Nano-mini-USB-Adapter-/190925303817

other 3 serial ports? i didnt realize the 2560 had more than one

and once the FTDI is connected how can i be sure the information will transmit through it instead of the onboard USB?