File - > New Playlist. Name your playlist (iPhone Sync)
Drag music from your ITunes Library (in iTunes) in to your new Playlist.
Plug your iPhone in.
Select iPhone in the DEVICES Menu.
Click on the Music Tab.
Check Playlist Name you created (iPhone Sync)
Check Include Music Videos
Check Sync Music
Click Sync in iTunes and your playlist will now be accessible on your iPhone
“NOTE:Any changes you make on your iPhone Sync playlist will alter your iPhone tunes too.”