I need to install a used hot water tank into an existing home that had
the tank already removed. So looking at the existing hookup is
impossible since no tank is there.

Two of the wires are hot, so I will simply attach 110V to each wire,
of course being on a separate leg off the box. Where does the neutral
wire attach? To the ground on the tank?

I've searched for a good illustration that described the electrical
hookups to no avail. And with this being a used tank, no instructions
are present.

Please let me know how to hook this up or please point me to a good
illustration on how to do so. Thanks in advance for your help!