All paper trading accounts start with 1,000,000 USD of paper trading equity. You may reset this equity at any time using the Paper Trading Account Reset page in Account Management.
Simply log in to Account Management with your paper trading account username and password, then click Trade > Paper Trading Account Reset.
You can also reset your paper trading equity in your production account. Log in to Account Management using your production account login credentials, and then click Manage Account > Security > Reset Paper Trading Account Password.