Withdrawal Request – My Account

I’m a noob to the site and theme but quite experienced with wordpress and another vendors auction theme (I have plenty of scars!) so forgive me if I’m missing something obvious.

In the Withdrawal Request part of My Account, how does the user come to get a balance in there to withdraw??

Ideally, I would like my users to load a balance into their account via paypal and then pay for either single listings fees by that or pay for a membership package via the user balance.

I can’t seem to find a way of tapping into the account/user balance aspect to facilitate this process.

Is this possible or can someone point me in the right direction of any documentation about the My Account functions?

Thanks in advance.