Need help wiring in a voltmeter that only runs when the switch is on

Hey guys small electrical project here and i'm not sure what the easiest way would be to wire in this simple voltmeter. The positive already has an inline fuse in it.

For the positive cable one way I can think of is to leech off of the wire that comes off the ignition switch that only has power when in the on position with one of those clip in wire splice taps. Do you guys know of a easier way?
The negative is self explanatory don't need any help there.

Bike is an 82 xj750 seca with an upgraded fusebox

 

hook the positive lead to the output side of the headlight or signal fuse.
best and easiest location hot would be the pink wire for the horn input cut the quick disconnect off and replace it with a new one.
or cut the wire and splice it in then cover with heat shrink.

you will also find a few bullet connectors in the headlight bucket that are hot and unused.

you could buy the correct connector to plug into it, or just pickup a bullet connector and replace factory connector.