The first place I would start is to remove the fuel line from the tank tap and then turn it on. If fuel flows out, that part is working. If it doesn't, that's one of the reasons the bike won't start.
I'm not sure about the kind of carburetor you have but most of them have a float bowl on the bottom that is attached with screws.
After removing the screws and any drain hoses connected to the bottom of the carb lower the bowl.
With the bowl removed, turn on the gas tap. Fuel should flow out of the float valve.
If it doesn't, jostle the float a bit and see if that can break loose the needle valve that the float pushes against.
If fuel starts to come out when the tank tap is turned on, turn the tap off, reassemble the bowl onto the carb and try starting it again.
If your lucky it will start.
If it starts, go to a auto supply and buy a bottle of Chevron Techron.
It's sized for the 10-15 US gal tanks on a car so pour about 1/3 of it into the fuel tank.
Start the engine and ride the bike a few miles even if it is running pretty crappy. This will get the Techron down into the passages in the carb so it can begin dissolving the varnish that has built up during the last year.
If it doesn't start, the jets are probably plugged.
This requires removing the carb. and removing the jets that are located in the float chamber and the needle valve that's located outside the carb body. After the jets are removed you can buy some dedicated carb cleaner and soak the carb in it.
Beware: Some of the carb cleaners can dissolve your carb as well as the deposits. Read the instructions carefully.
Hopefully, someone who is more familiar with the exact carb your bike has will join in and give some more detailed instructions on cleaning the jets and resetting the needle valve on your carb.
If your careful in all of this, the old gaskets should be reusable.