If you navigate to your TradersPost paper account, you will now see a new "Reset" button that you can click which will take you to a form that lets you specify an amount to reset the balances to.
You can also check the "Reset positions" and "Reset orders" checkbox to clear the open positions and order history from the account.
We are looking forward to continuing to improve the internal paper trading functionality at TradersPost. Our goal is to make it the most flexible, intuitive and feature complete paper trading system in the world!