I have two of these. One for the fridge and one for the other outlets I wanted powered.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
If your knowledge of electricity is a few steps beyond basic and want to save a couple of $$, the switch is actually a double pole, double throw relay with contacts rated for 120VAC 15 amps and a 120 VAC coils. The relay is energized by shore power so you could just leave the inverter on and anytime shore or generator power is turned off the inverter automatically takes on the load. Install in the circuit after the breaker panel.