Struggling with the gauge wiring, wording below for the volt gauge mentions certain Mustang production years, I’m using a new complete kit. Where do I attach the yellow wire on the gauge?

From installation guide"
Volt Gauge
Attach the yellow positive wire using a butt connector to the power wire feed as described below.


Power wire
90-93 Attach the red wire from the power distribution cable to the Mustang gauge pod Ign. Sw. to
Ign. Coil (BATT) wire used earlier for the charge indicator.
96-04 Attach the gauge red wire to the gauge pod Voltage in Start and Run (white/light blue) wire.

Also, the fuel gauge shows full when empty and when a couple of gallons of fuel is added it moves to 3/4 full, what am doing wrong??