the instructions that come with a Trucklite / Signal Stat 900.

https://photos.app.goo.gl/YWBowrhUnoURXUpC8

They are made to use the stop light filament in the rear and their own filament in front. If you don't already have a double contact bayonet socket for your parking light, you will need something like this.

tps://www.zoro.com/grote-lamp-socket-pigtail-68130/i/G1038502/?recommended=true