Eagle - How to attach a pin not shown on schematic symbol?

"Invoke" command resolves this.

I've got only Eagle 5.11.0 in front of me at the moment. But, this haven't changed in 6.3.0

@ScottSeidman had beat me to the answer, while I was annotating the screenshot.

You use the INVOKE button. It looks like four AND gates with an arrow on the lower left one. It will let you hook up pins that are attached to default nets.