To get a snorlax you need to train up a munchlax. Munchlax are attracted to the sweet smelling trees with honey on them but are VERY rare. So once you've got your munchlax train it up but also focus on keeping it happy once its at peak happiness once you level up it will evolve.
Put honey on a tree and wait until you get a munchlax. Catch it and give it a bunch of proteins and stuff then level it up until it evolves.
Level up a munchlax witch is really rare to catch when you put Honey on a tree also you need to feed it lots of proteins and keep it happy!
Snorlax is gay