How do I refill a gas powered snowblower?

Most walk behind snowblowers were gas powered; petrol (can’t think of any diesel) best fuel in non-ethanol fuel – - mid-range.

All gas powered equipment, like lawn mowers and snow blowers, are designed to run on regular unleaded gasoline of 87 octane. It usually says so on the fuel tank.
(Diesel fuel, by the way, would not be a good fuel for manufacturers to use because the fuel sets up like Jell-O in really cold weather. A special additive, anti-gel, is used in these instances.)

You fill up a 2 or 5 gallon gas can at the gas station, schlep it home, and pour it into the snowblower.
Check the oil level before you operate it. Some have a dipstick. Some have a sight glass.

If it has been sitting I pull the cord gently a few times to get the oil flowing a little, before really trying to start it.

^Is schlep a New York term? :-)

^ Absolutely. It is best said in a Long Island accent with a hint of kvetching.
A 5 gallon can of gasoline weighs about 35 pounds. That is a schlep!