Add a circuit?

The cover for my fuse box is long gone.

A head unit should only need power and ground to turn on? I cut the wires from the old head unit and i cant get the new one to power on so i hooked
the old one back up and now that one will turn on but the screen is super dim and wont do anything?

Used the add a circuits and all is well now. The wire wrapped around the fuse prong must not have been getting a good
connection.