VDO Gauges do not come with wiring instructions, so......
The two large poles are used to hold the 'U' clamp that keeps the gauge in position and do not have any wiring attached to them.
The small pole that has a 'G' next to it is there so that you can attach the wire that is being run to the sender. Remember that the sender must also have a wire running back to negative on your battery. This could be the earth strap on your engine if it runs back to the battery.
The small pole that has a '+' next to it needs a (12 volt or 24 volt depending on gauge type) live feed from a switch and fuse. The gauge will draw 1.25 amp max.
The small pole that has a '-' next to it returns to your battery.
The red wire provides power to the gauge internal lamp. This requires 12V feed from a switch and fuse and will consume 0.05 amps when running.
Please note there is no wiring for the internal lamp negative. there is internal wiring that takes that to the correct pole.
Please note. The Battery gauge - Volt gauge (12 or 24 volt) will only have two poles, so no 'G' pole.