To delete an account you need to go on the settings page: 

https://dashboard.publit.io/app/dashboards/settings?account

At the bottom of the page, you will see the Delete master account button (If you are on your main account). You just need to click this button and fill in your password and the reason for deletion. Once you click the Remove account button your account will be removed.

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).