It's in the manual. Here's a link:
http://www.usfirst.org/uploadedFiles...t_data_enc.pdf
Look at area A/B 4 on the diagram and you will find the signal light. It gets connected to the Digital Sidecar RSL terminals. Make sure you have the polarity correct. It also appears the two positive terminals on the signal light connect together to a two wire feed that runs to the digital sidecar.