As said. Look for critters. Clean out nests and cobwebs. Look for chewed wires, hoses, cables. All good? Drain the gas tank completely. Rinse out. Drain the oil tank completely, rinse out. Pour in 1/2 tank of fresh new fuel and 1/2 tank of new oil. Open the fuel valve, turn on the ignition, pull the cord. Get it to light off. Take for low rpm rides around the property to get everything moving and turning. Stay close to home, walking distance. Once they prove to be runners, there are a bunch of things that will need attention before taking them out for a day of riding.
Start with the basics: Do they run as is? Get them to prove it first. Then put the time and effort into all the other things that will need to be done before deemed ride-ready.