Lighting, Light Fixtures, Ceiling and Exhaust Fans - ceiling fan and light on one switch

I don't know a whole lot about home wiring, but I'm wanting to put our ceiling fan and light on two switches. We have the one switch right now. I was looking in the box where the switch is, and there are two main wire groups coming into the box. One has black, white, copper. The other one has red, black, white and copper. The whites are connected together, all the coppers are together (which are ground, correct?), the black from the 4 wire group is capped, and the red and black from the 3 wire group are connected to the switch. What would I have to do to add a 2nd switch to control the fan power? Do I have all the wires there that I need? Is the 4 wire group from the fan? or the 3 wire group? Please help me out if you can. I appreciate it!!!!

You have made a mistake in your description.

These two statements are contradictory:

"...there are two main wire groups coming into the box. One has black, white, copper. The other one has red, black, white and copper."

and

"...and the red and black from the 3 wire group are connected to the switch."

The red and black are from the four wire group, not the three wire group.

You MAY have the wires you need, but to be sure, please report on the proper wiring at the switch and also please report on the wiring at the ceiling light/fan.