Q: How do I download/install an app when my phone doesnt let me????

Try resetting the App Store:

Close the App Store completely from the app switcher window by double clicking the Home button and swiping up the App Store preview pane until it disappears from the screen. Then sign out of the iTunes Store (in Settings).

Then do a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears.

Then sign back into the iTunes Store.

Also try going to Settings > General > Restrictions > and make sure that the iTunes Store, Installing Apps, Deleting Apps, and In-App Purchases are all under the Allow section. Test installing again.

It sounds as if your account may have some hold on it, and will require contacting iTunes Support. I would recommend contacting AppleCare during normal business hours to resolve this.

Contact Apple for support and service - Apple Support