When trying to download music from Apple music

Hi I am subscribed to Apple music and I have quite a large library which consists of a lot of songs I have added from Apple music plus some of my own. Everything is sinced but when I try to download it on to my Iphone 6S, while it is in my library on the phone and on my windows PC it will not download on to the phone, it just says download waiting and a button. When I press this, it goes back to saying, download. How can I get it to download on to the phone permanently so I can play music off line, which is what I thought one could do if you were subscribed to Apple music, it's fine while I am on wifi but there a way I can get the songs to download to the phone, even if I add them from the phone to the library first....They add perfectly....This sounds complicated but is not meant to be smile.