Ask to buy doesn't appear as a prompt when I select my child's account. How do I change the settings so that they need my approval to purchase an app.
See above
See above
The child is under 18 ? If the option isn't showing (Request and make purchases with Ask to Buy - Apple Support) contact iTunes Support : http://www.apple.com/support/itunes/ww
Ask to buy doesn't appear as a prompt when I select my child's account. How do I change the settings so that they need my approval to purchase an app.