Kitchen Large Electric Appliances - Dishwasher Drain

Ok, I'm installing my first dishwasher. Everything is going fine but I have a question about where the dishwasher drain should be going.
The old washer went to the drain from the kitchen sink right above the p-trap. There is a little copper pipe that sprouts out from the main copper pipe from the sink above. This side of the sink is closest to the dishwasher.
The new dishwasher says that the drain should go into the garbage disposer. I see the where it should connect to the disposer and it will reach it.

Should keep using the current drain or use the other side with the garbage disposer? If I use the garbage disposer side, what do I do with this small open copper pipe?

Thanks,
Shawn

You can use either. Both will work, if you use the disposal side you will need to remove the knockout plug in the opening and then plug the copper tube to keep it from leaking. I would just put it back on the copper drain the way it was before, unless the copper tube is too small. Doc E

Thanks. Unfortunately the copper tail piece is too small so I'm going to drain it to the disposer. What do I cap the capper tail piece with?

Also, it turns out that my power is about 6 inches short from the terminal box on the dishwasher. Can that be extended? Or does new wire need to be run to it?

Thanks,
Shawn