oh sorry. I'm not sure about all this and thanks for clearing it up. so about 1000Ohms will give me 20mA. Does sinking mean i connect the negative to the chip and positive to my own voltage source?
Output pins wire to the cathode lead of LED and the anode lead would wire to the voltage source. Calling the leads negitive and positive for LEDs is a little 'simplistic'. 
Lefty