In the spec you give
208v 3phase/110v., the number 110v indicates that this 3-phase generator is set up as Wye configuration. This is perfect for you. You will hook the common neutral to your house panel neutral and any two of the three, three phase power outputs, one each to your 120 volt house legs (
phases ). The 3rd output on the generator will be left not used. The voltage at any of your 120 volt panel brakers to neutral will be normal 110 volts but the so called 220 volt as measure between the two hot legs will be less than the sum of 110 +110 volts. It will be closer to 208 volts. This ought not be a problem. In this setup the generator will only produce 2/3rds of the available 3-phase nameplate power or about 9 kW.
If you want to be clever, say you have an outbuilding or yard lighting circuits that could use 110 volts single phase only power when the genset is running, you could run from the generator common neutral and that third unused leg (110 volts to neutral) to your outbuilding. That way any power used in the outbuilding will not reduce the 9 kW capacity of the house circuit. The power available to the outbuilding would be a maximum of 1/3rd the nameplate or 4.5 kW.
See, easy as pi.