I am preparing to add recessed lighting on my boatdock in the soffitt. I have wires running to light switches that I can splice off. I am not sure exactly how to marry one wire and make two in order to wire the recessed lights. There will be six of them. Thanks

You will need the correct connectors for the cable/conduit you use.
If romex, use a romex connector to first box, another cable out of their to next light, and so on. Last fixture will only have 1 cable, the rest will have 2.
Green or bare to bare, white to white, and black to black(or switchleg color).

Thanks!