How to sync an iMac's music to a new iPhone 7

I have an iMac with music on it and when I had my iPhone 5s all I had to do was plug it into my iMac and go through what I wanted to do and it downloaded what I waned to my ipPhone. However, with my iPhone 7 when I plug it into my iMac nothing happens, it just sits there and does nothing. Surly there must me a way to transfer my music from my iMac to my iPhone and any help would be greatly appreciated.