Since I've had to send this to a dozen people in the last week and it's by far the most common question we get:
If you're wondering how to join the Patron-Only Discord Server you need to link your discord account to your Patreon account to have the Patreon bot invite you to the server and manage you. The location of this option is in your account profile (bottom left on the current UI on my PC.) You'll go to Settings > More > Connected Apps and add your Discord info there. At that point Patreon should take care of the rest within a few minutes. The bot kinda sucks though, so it may do whacky stuff, don't worry we'll help you get sorted from there.
If you're a Swaglord or higher it's VERY important you join the Discord as most of your bigger perks are handled through there, not Patreon. And if you ever screw up and get yourself banned you'll lose out on those benefits.