Copying songs to iPhone
How do I copy selected songs from iTunes on MacBook Pro to iTunes on my iPhone?
iPhone 5c, iOS 10
Question marked as
See here: Sync music between your Mac and iPhone or iPad - Apple Support
Make sure "Selected playlists, artists, albums, and genres" is selected in Sync Music Settings as explained in the link above.
Then either drag an item from the library onto the iPhone on the iTunes sidebar, or uncheck anything in the library you do not want synced, and keep anything you do want synced checked and click on the Apply button to sync them.