To delete an account you need to go on the settings page.https://publit.io/dashboard/settings
At the bottom of the page, you will see the delete button. You just need to click this button and you will delete your account.
Ps. If you delete an account there is No undo action (all your info, billing stuff, invoices, files, file versions, players, ad tags, watermarks, and stats associated with this account will be deleted permanently).