Go to the Cockpit page. In the main menu, click on "Cockpit" to access your account management interface.
Select the account you want to flatten. In the "Accounts" section, locate the account you want to flatten. Click on the "Flatten" button associated with that account. Do note that individual flattens work on a per contract basis, be sure to flatten the contract with orders pending.
Flatten all accounts
To flatten all accounts select the big red flatten all button in the cockpit.
Important note
Flattening an account is irreversible and will result in the immediate closure of all active positions. Make sure you want to proceed before taking this action.