This is the unit I put in our new Sunseeker:
PD5110010 120 VAC 30-Amp Automatic Transfer Switch.
There's two inputs and one output - one input used the terminals in NC (Normally Closed) position, the second input energizes the relay, thus those are NO (Normally Open). A circuit module built into the unit delays the output transfer for 20 - 45 seconds.
Download the owners/install manual:
Installation and Operation Guide for PD5100 Automatic Transfer Switch I put the generator on the NO input so it would energize only when the generator was running. The shore cord connects to the NC inputs, thus the relay is not energized. The generator will be used for about 0.5% of the time vs connected to shore power.
The terminals are labeled for the various inputs. You shouldn't have any difficulty installing it if you are comfortable with basic wiring.