To delete your account go into your Settings and choose "Delete Account".
You'll be required to enter a password, but if you didn't create one while signing up (i.e. you logged in via Facebook), you'll need to set one up first. This is to ensure that you don't accidentally delete your account and lose all your content.
Deleting an account honors also your “right to be forgotten” as defined by the Art. 17 of the European General Data Protection Regulation (GDPR): any personal information tied to your account will be removed within 30 days.