Go to your account settings page, and tap the "Delete Account" button which will look something like this:
Please note, if you delete your account:
Once you delete your account, you’ll be logged out of this app. If you are logged into the app on any other device, it can take up to 1 hour for your session to expire. To access your order information after you delete your account, contact us. If you change your mind, you can always sign up for a new account.
You can also contact us by submitting a ticket on our support page, requesting your account deletion.