Lighting Install

It means to connect the "copper wire", whatever wire that refers to, to the bare wire of the supply circuit using a wire nut or equivalent (assuming of course that your supply circuit has the normal ground wire--if this is an old house with pre-1970s or so wiring, there may be circuits using ungrounded cable, and in this case you won't be able to produce a ground). If you mean just attaching the "copper wire" to the box will provide a ground, this is not generally true, and even if the box is grounded it is not an acceptable way to ground the fixture. The circuit ground conductor needs to be directly connected to the fixture ground wire; the box also needs to be connected to the circuit ground unless it is a plastic box.