This appears to be a subpanel, so find the panel that is feeding this one and shut off its feed there by flipping the proper breaker off. Also, note I'm not a pro at this, it appears that this panel is deficient in that as a subpanel, it is required to have a four-wire feed with separate neutral and ground leads; you only have a ground lead, which may be tied to neutral back at the main panel, but should be separate here. If you don't have a proper neutral, you can't make any 120vac circuits, as the ground lead should NOT be carrying any current except in a fault situation. That, along with the fact that it is not insulated makes for a major problem. I don't think the panel would pass code, even when it was installed, let alone today. But, again, I'm not a pro and may be missing something.
One of the pros will either verify or reject my assessment...I think I'd call a pro and do some rewiring to make it safe and get what you want. That uncapped big hole on the side of the panel isn't a good thing, either.