Plug the end of your transducer's cable into the port on your transducer extension cable.
Plug the other end of the extension cable into your transducer's connector holder. Attach the connector holder to your transducer's mounting bracket, and fasten the holder to the bracket by using a screwdriver to drive 9 mm screws into the bracket. Slide the mounting bracket into the receiver.
Turn the receiver on to test your extended cable. You can now get proper readings on the receiver.