Purchasing iTunes music via iPad.
Why does it appear that I cannot purchase music from iTunes on my iPad air 2? The iPad syncs all of my previously purchased music (on my iMac) fine and the music seems to play fine. I did once (in 2010) purchase an album on an old iPad that then synced to my iMac and stayed there but cannot seem to figure out how it is done now. Any assistance would be appreciated. Thanks!
iPad Air 2 Wi-Fi, iOS 9.0.2