Please...need some help.

I am trying to add a receptacle in my garage. The easiest run is to come off a light that operates a two way switch, tie in and drop the line from there.

Here is where I donít know what to do. Inside the box there are 3 white wires tied together with a leg going to the light, 1 Red with going to the light and 3 black wires tied together wire nutted (is this a word?) off. Do I tie the new run to the (white and red,) (white and black) or (red and black)?

Thanks for sharing your knowledge!