I don't see one on the motherboards I\O, if your case has one on the front you can find that cable and connect it to the 1394 plug on the mobo itself. Check the manual to find this plug, I couldn't find it by zooming in the pictures on newegg.
The ASUS P6T6 does not have an IEEE 1394 connector. You would have to get a USB 2.0 to Firewire adapter.
From the manufacturer spec sheet:
24-pin EATX Power connector
8-pin ATX +12V Power connector
CPU fan with PWM control
Chassis fan1 with Q-fan control
Chassis fan2 with Q-fan control
Chassis fan3 with Q-fan control
CD audio in
3 x USB connectors support additional 6 USB ports
20-pin Panel connector
Front panel connector
S/PDIF Out header
There's no IEEE 1394 connector listed. A Google search turned up posts on several different forums where people were complaining about this.