Could you give us more details please? Is there an error that comes up?
Does it look like it has been added in iReal Pro>Settings?
I presume you are connected to internet?
Did you purchase it with your same iTunes account you bought the app in?
Can you turn your device off completely, then on again, then in your device's Settings make sure you are connected to your Apple account (Settings>iTunes and App Store), then check in iReal Pro.
Thanks.