To request your account to be deleted, you can go in-game and access "Settings" by tapping on the three bars hamburger menu on the upper right-hand corner of the screen and going to the gear wheel. 
From the Settings menu, you can select "Manage Account" and select the "Account Deletion" option directly. 

If you’re currently on our web portal, open a ticket with our support by using the chat icon, and they will be able to assist you with your account deletion request.