Instructions
Press the "Power" button on the PS3 to turn on the console. You can also press the "PS" button on the controller to power on the console.
Select your user account and press "X."
Select the "PlayStation Network" icon. Sign into your PSN account if your system isn't configured to automatically sign in on startup.
Select "PlayStation Store" from the PSN menu and press "X." The PlayStation Store screen will appear.
Select "View Cart" in the top, right corner of the screen and press "X." The "Shopping Cart" screen will appear. The PSN account's remaining wallet balance is next to the shopping cart icon at the top, right corner of the screen.