why cant i move music from my itunes library to my iphone

How are you trying to move the music? By dragging? If so, have you checked the "Manually manage music and videos" in iTunes?

How do you change that setting?

1. Connect the phone to your computer
2. Wait for it to appear in the list on the left side of iTunes
3. Click once on it in that list
4. Look to the right and scroll down to Options - one of the checkboxes says Manually manage music and videos

its not working i tried the (add to) option doesnt pop up im real frustrated

you want to make sure that itunes is up to date and so is your phone and that both are sign into the same apple id if you have to up date itunes make sure you rest start you computer if that does not help call 1800myapple