Sony Ericsson Xperia Arc — disable in app purchases in xperia arc s??

Hi,
I can´t find where I disable in app purchases in xperia arc s?
Anyone who knows where I do this?

Thanks!

Disable app purchases? You mean on Google Play?

You can set a pin number for your google play app, so that only you can make purchases. Open the play app, go to settings, then tap "Set or Change PIN". This will keep children and friends from making unauthorized purchases.