signal lights added to 1936 Fordor

[Orignal36]

I checked through the posts. Lots of bits and pieces on this subject. But nothing that helps a newbe understand the process. Does anyone have an actual step by step on how to add signal lights in? My car came with two kits from Macs (attached). The car was converted to 12V with an alternator. I would like to stay with the original tail lights. The instructions in the kits help with mounting, but where do I tap into the harnesses? What gage wire do I use? Where is the best place to tap into the harnesses? I truly appreciate the help!
Thank you in advance,
Lou