Wiring help

Ok so this is the diagram. The green is the 5V trigger. It will turn the LED on, on the relay just doesnt have enough power to actuate the relay. I was reading about using a transistor with an external 12V supply but im not really sure on how to do that. If i take the trigger on the board and put it in the base of the transistor im not sure how to wire the emitter and collector.