I am trying to install a new light fixture to an older existing box. The box is copper, the fixture is aluminum. How do I attach them safely? Also I have two grounding wires coming into my box. Is that normal? Do I need to attach both of them to the grounding wire on fixture is do I need to attach them to separate things?

remodelmom,
When you say the box is copper... do you mean the wiring in the box is copper or is the box itself actually made of copper?
As far as equipment ground conductors go all of them should be connected together along with attachment to the electrical box if it is made of metal.

I have never seen a new fixture with aluminum wire. It may be plated copper that looks like aluminum. Is the fixture wire set clear or black and white? Attach all the grounds together and pigtail a ground to the metal box.