On the VT Markets App, you can easily transfer funds from one trading account to another trading account (under your own).
To do this, navigate to the "order page" and click on "more" and then "transfer".
Please note that the account from which you are transferring funds must not have any credit bonus associated with it, and both accounts must be denominated in the same currency.
Click this article for the guide on how to remove the credit bonus on the account.