Welcome to the forum.
The answer might well depend on the music.
In PrE 12, one would use Add Media, from say the HDD, with WAV mucic.
From a CD, with the music in CDA format, another program, such as the free Audacity, would be used to rip the CDA, then Save as PCM/WAV @ 48KHz 16-bit, for Import.
iTunes can present unique problems, depending on many factors. If simple Import, via Add Media, does not work, then please give us the full details of that particular iTunes music.