Along with iOS 9, Apple released iTunes 12.3 on Wednesday. The update for the media management and streaming music app added two-factor authentication support for Apple IDs, along with iOS 9 and OS X El Capitan support.
iTunes 12.3 comes with security updates and bug fixes
The 12.3 update also improved VoiceOver support for Apple Music, fixed an issue that prevented reordering of Up Next songs, addressed a problem with radio stations not appearing in Recently Played, and fixed an issue where "loved" songs on iOS didn't appear in "loved" in iTunes.
iTunes 12.3 is a free update and is available via the Update tab in Apple's App Store app.