go to the right of the screen at top of the page.

click on the down arrow then select "account settings" then select "account deactivation".

In addition to John's answer, I would say you can't delete your account permanently. You are allowed to deactivate your account for the time being and you can activate it again by email verification if you want in future. 

In a nutshell, you can deactivate your account but not delete your account permanently.