Fuel Gauge problem

Hi, im hoping someone can help. My fuel gauge isnt wired up on my 1963 beetle, i have found a single yellow wire from the sender but the back of the speedo has 2 connections for the fuel gauge?

From what I remember the wire from the tank sender is a ground, the other connector should be for an ignition 6V+ source, usually a red wire.

never hook a positive wire to the sending unit!