You install a breaker, depending on the watts of the inverter, in your main panel and run it to the " in " connection.
Then you run a wire from the inverter " out " connection to a new sub panel. The things you want to run on inverter are moved from the main panel to the sub panel.
That inverter isn't designed to be wired into the RV shore powers 50 amp 120/240 volt service. You would need a 12,000 watt inverter to do that.
Here is a layout that is typically used. Its a magnum inverter with 240 volt capabilities but I posted it just so you can see the way most are wired up.