Fresh water tank gauge wiring

[Danny Z]

Hi there,
I have a 76 tradewind that came already gutted. There is a brown and red wire that come into the interior from the fresh tank (the sensors splice into them. I bought a new gauge that has a single wire to attach to the sensor. Can anyone help? Is the red wire what I should attach to it? Do either of these wires need to be attached to 12 volts? Am I totally wrong about all this? I read on other threads about the wiring harness to the control panel, but none of that is still around on my trailer. Just the red and brown wires.
Thanks