The asset field is where you pick the security you'd like to backtest. You can enter the full ticker symbol of the security directly, or you can search for it in the field itself. Currently Tradewell supports equities, ETFs, commodities, crypto currencies and forex. Just start typing the name or first few letter of the security in mind, and a dropdown many will appear with a list of likely securities. Click the name of security you want to backtest, and it symbol will automatically load in the asset field.