Getting it to run should be simple, getting it to run well, that could be a challenge.
The bike needs, air, fuel, and spark to run. Be systematic and check them out.
Spark is the easiest to check for. First, make sure the battery is fully charged. Remove the points cover. Rotate the engine with the kick start lever, do the points open and close? Get a multi-meter or circuit tester and make sure you have power to the points. If you do, pull one spark plug. Attach it to each of the 4 caps in sequence, touch it to cooling fins (I prefer to use rubber handle pliers to do this) and turn the bike over with the starter. Is there spark at each plug? If yes then move to fuel.
Unscrew the float bowl drain screws, is there gas in all 4 bowls? If yes, then you have fuel to the carbs.
At this point you have spark and fuel to the carbs, the most likely issue is that the jets are clogged from sitting and you will need to pull the carbs off, clean them and install new rubber seals.
However, another approach to try at this point, just to get it to start, would be to remove the air box so you can get to the carbs and to disconnect the fuel hose from the petcock and drain the gas in the float bowls and then re-tighten the screws. Attach a small funnel to the fuel line and poor some fuel system cleaner into the funnel to fill the bowls with cleaner. With the airbox out of the way you should be able to fit the red plastic tube from a can of spray carb cleaner over where the jet protrudes into the venturi of the carb and spray cleaner down the jet to help clean it out.
This isn't a substitute for a proper cleaning, but may let fuel flow enough to start the bike.
