Voltmeter wiring help

[Gerkin]

Simple man looking for a simple answer (Hopefully)
The back of my Voltmeter gauge has 2 terminals besides the ground and lights.
There's an S (which I am assuming is sender) and it has a red cap on it.
The other Terminal is an I (which I am assuming is Ignition)
Simple question. What wire should go where?

Thank you very much for any help

 

[alldodge]

If this is the way you found it (red plastic cap on S terminal) then purple wire goes on I terminal and your good

 

[Gerkin]

Well c'mon now. That is too easy
When I got the boat there was no wiring and trying to google wiring a voltmeter all I got was huge wiring diagrams.
The purple wire goes to the IGN on the switch so that makes sense.
I figured there was more to it.
Thank you very much

 

[ARJOE]

I terminal is voltage in, or what voltage you want to measure. Typically comes from ignition.
S is signal/voltage out. Typically not used on a volt meter.