Good morning docfi,
Welcome to the Apple Support Communities!
If I understand your question, it sounds like you are trying to sync the music in your iTunes library from your MacBook Air to your iPad. I'll provide some resources below with information about USB syncing and playing your music, including the "Up Next" playback option. I've highlighted some key information here for you. Click on the link for complete details.
Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB
iPad User Guide - Play Music
Control playback. Tap a song to play it and show the player. Tap the player to show the Now Playing screen, where you can do the following:
Tap 
to return to the song’s beginning.
Double-tap to play the previous song in an album or playlist.
Quickly navigate to the album. Tap the artist or album name under the song title in Now Playing.
Hide Now Playing. Tap 
at the top of the Now Playing screen.
Add a song to your library. Tap 
.
Access additional options. Tap 
.
See what’s up next. Swipe up. Tap a song to play it and the songs that follow. Drag 
to reorder the list.
Get audio controls from the Lock screen or when using another app. Open Control Center.
Stream music to a Bluetooth or AirPlay-enabled device. Tap 
in Now Playing, then choose a device. See Connect Bluetooth devices and Stream audio and video to other devices.
Enjoy!
