In order to Top-Up your NAGA One using the funds from your trading account. You must click on the Invest icon on the bottom of the main screen
When you are in the main screen of the Invest you will need to drag the bottom part where the amounts are showed. Then you can select the trading account and click on the '+' sign.
Instead of choosing "Credit Card" click on the menu and select the Trading Account you would like to transfer the funds from, as the payment method, enter the amount and click "Add money".