Server deletion, like channel deletion, is a pretty simple process. Here goes:
1. Open up your server settings tab by clicking on the Server Name box:
2. Click 'Delete Server' at the bottom of the left hand menu, and affirm the server deletion. Boom!
Note: Only the Server Owner has the power to delete it, regardless of the permissions assigned to any role.
Double note: If you have 2FA enabled on your account, you'll be required to enter in your authentication code before deleting your server.