Go to Account Settings and scroll down until you see the button «Delete Account». After you click on it, you will be asked to provide a reason why you are leaving the site – you found someone, it's too expensive, you didn't find anyone interesting, etc. Then you should confirm the action by clicking on the respective button. All your data will be deleted from the site, and it will be impossible to restore it. However, if you would like to delete your account only temporarily, you should click on the button «Disable Account» instead of instead «Delete Account» in the Settings.