How do you mix the gas in a 2 stroke dirt bike?

First, you find out the gas-to-oil ratio recommended by the manufacturer - that is critical. Too much oil, it will run poorly, foul the plugs and smoke like crazy. Too little oil, and you will burn up the engine. The buy a bottle of two-stroke engine oil. There is a mixing chart on the back label for whatever ratio you need. Put the amount for one (or five, whatever) gallons in a clean, empty gas can, then add the correct amount of gas for that amount of oil. Close, and shake well. Then you are ready to fuel up.