i take it you know where its located too?
get some carb cleaner/brake cleaner or similar and a cloth
locate throttle bodie, find where accelarator cable meets, here you should be able to open the butterfly valve manually by pushing the cable down.
spray in cleaner, and use the cloth to wipe off as much as you can, beyond the valve to, be carefull not to let your finger get trapped,
you can also blast some down through when engine is running but id prefer not to.
usually after initial fire up, youd have a little white smoke, soon burn off