Using Rx_Tx on the I2C Line Following Sensor

Am using an two I2C Line Following Sensor http://www.robotshop.ca/summerour-line-following-sensor-3.html and am using an arduino decimila, i need to connect one of the sensors on the analog pin 4 and 5 (i2c) then i use the other sensor on the tx_rx since the sensor have both the rx and tx options.
I know how to use the sensor on i2c i.e. while connected to pin 4 and 5 but i don’t know how to go about the same while on the rx_tx section.
If anyone has an idea of how this is done i will be very greatful.

Kind Regards,
David.

Youv'e made a mess of posting that link and it just returns "bad request" can you hit the modify button and edit it so it works.

As the serial data is used for uploading and debugging you might be better off using NewSoftwareSerial to do the communications.