Eagle and polarity ?

I am using in our Eagle pcb this light sensor :

This sensor is a regular 0805 package , but it has polarity (emitter/collector) .

In Eagle, I just use a resistor of 0805 , but how do you set a polarity to this part in Eagle? How the machine would know the placement if the part itself has no polarity signs on its pads/I can't see them on the DS.

Thanks.

(deleted)

Or make your own symbol. This set of slides will guide you thru the process quickly.

Slide1.zip (494 KB)

Make new library part, and include some polarity marker on the silkscreen when you create the package.

Thanks very much guys. I never did this before but will try.