What do you want to do? If you want your UNO to be a USB2Serial device you can just connect it via USB to your PC and connect the TTL serial device to pins 0 and 1. Voilà, you have your USB2Serial. You don't need any software to be run on the UNO, it acts as a USB2Serial converter.
If you need something else than a USB2Serial converter, tell us what you want to achieve!
Thanks Pylon, sounds simple and yes that is all I want to do is to send data to my serial device
from my PC and to stream TTL serial data from that device to the USB port as I can have my Lab view application parse the data...
Does this require any code on the Uno to set up the pin 0 & 1 lines?
What would the code look like if there is code needed?
(regarding the TTL levels- I am using a Max32222 chip to interface between the ardunio Uno and the serial port of the device.)