Simple Wiring help

[Kmccaslan]

I am tyring to put a new brake light/tail light on my bobber project. It is my final piece for now. The issue is wiring it. I can make it a taillight and I can make it operate as a brake light, but not both. It is a trailer light and only has two wires. I am splicing into a blue, yellow, and black as most of you already know. Any help you guys can provide will be greatly appreciated.

[oseaghdha]

Just figure which wire is the running light(BLUE) and which one is the brake light(YELLOW).
Ground the (BLACK) to the metal part of the light assembly.

[randy]

Is it a dual-element bulb? if so, follow oseaghdha's advice. If not, you're SOL. You need a dual element bulb.