I want to put electrical outlets into a garage connected to a 40 year old house. First of all, the only wiring currently in the garage goes to a light socket. This wiring is somehow routed from the porch light because it only works when the porch light is on, therefore I think I need to install a 3-way switch into the porch light so that the electricity in the garage will always be on. Can I just splice the wiring from the light that is already in the garage and then route it to the desired electrical outlets? My second question deals with the ground wire, there isn't one in this old house that I am aware of. All of the current electical outlets only have the 2-prong boxes. Is this going to be a problem when wiring the garage? What do I need to do to add a ground? Thanks for your advice.

I will be connecting into the existing meter to the house for the new separate garage (with upper hobby room) 125 amp breaker box. I have run 2 #2 THHN, 1 #4 THHN, and 1 #6 bare copper from the meter to the new garage panel. So the #2's will go to breaker cutoffs, and #4 will go to neutral bar. Where does the #6 bare copper attach to the new breaker box? Do I also need another bare copper attached to the breaker box frame and down to a ground bar on the outside of the garage?