You join the website and the discord.
You can buy the adopts that are put for sale, buy an myo slot with real money, or solely gather enough leaflets to buy one from the website shop.
You'll need 8000 leaflets for that. After a year, I finally got enough for one.
Snekkets myo unfortunately can only be bought with real money, so if you can't afford one, like me, you'll probably not get one at all.
Unless you participate on the current event where you get a Snekket MYO. I unfortunately didn't make it, but I'm sure that you will.