First things first.... put some regular fuel in it, run it for about 10 minutes, and then drain the engine oil and replace with some good synthetic 5w-30 motor oil in the crankcase. Not sure if it takes 1/4 qt or about a 1/2 qt per oil change. Oil needs to be hot, hot hot and mixed up/homogenized from running before draining out and replacing.
Additives to fuel... Stabil should be in the fuel, 1 oz per gallon, or get a 6 pack of Chevron Techroline at Costco. Needed to keep the jets unclogged if you don't use the generator regularly. Read the label for mix ratio.