Itunes on Ipad

If you've added them to your computer's iTunes library, and if the computer and iPad are connected to the same wifi network and have home sharing enabled using the same account on both (Settings > Music on the iPad ; File > Home Sharing on the computer), you should see the music under Home Sharing in the iPad's Music app for streaming : Use Home Sharing to share iTunes content with other devices - Apple Support

Depending upon your iTunes' settings/preferences you shouldn't need to copy the music onto the computer, it should be able to pick them up from the drive and stream them from that to the iPad

See Use Home Sharing to share iTunes content with other devices - Apple Support. You can access the iTunes library, which in turn uses the tracks on your network share, but it can be slow to access your library there, and of course only works on your local network. You could create one or more playlists of your favourite content and sync that to your device with iTunes so that you don't swallow up all its capacity.

You could also potentially use something like Plex to play media from a shared network location, but I suspect it isn't ideal for music.

tt2

Can i only play music that are stored locally on the Ipad?

You can stream, via home sharing, music from your computer's iTunes library. Or you can stream music stored in the cloud.

Not possible to add files/folders from a network folder to the library?

You can add music to your computer's iTunes library and then sync or stream it to the iPad

If you want the music stored in the iPad's Music app then yes, select what you want to copy over to it and sync : Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB - Apple Support

You should find a Computers section in the iPad's Music app.

It isn't possible to add content to the Music app the is stored anywhere other than on the device or in Apple's cloud service for your purchased music and/or iTunes Match or Apple Music collection.

tt2

If you want access to all of your songs on your iPad, without copying them to the device, then it sounds like your want either iTunes Match or Apple Music. Both services allow you to create an iCloud Music Library from which content can be streamed or selectively downloaded for offline use.

tt2

Obviously one of the changes in iOS 11 I haven't paid proper attention to. When the device is on a network with a suitable shared library Home Sharing appears at the bottom of the list of sections of the library in the music app.

tt2

What is the setting in iTunes Preferences for "copy to Media folder"?