But doesn't installing a internal gps void the warranty?
Theoretically yes it could. So far, there hasn't been a test case of a modded radio breaking and needing warranty service. I've asked UPMan about it, and he was not able to give me a definitive answer. It would probably depend on exactly what the malfunction was, and whether there was any plausible way to blame the malfunction on the modification, but until there is a test case, it's theory and conjecture. But I advise potential customers to assume the warranty is voided.
Regarding the OP's question, if he got the correct cable, there's only one way to use it to connect between the scanner, the GPS puck, and USB port. Plug the connectors that match together, verify the light on the GPS puck is turning on, and scan either the full database or favorite lists that have Location Control enabled, and the rest is automatic.