How can I get my Samsung Galaxy S6 connect with Android File Transfer?

[AC Question]

I downloaded Android File Transfer and tried connecting my Samsung Galaxy S6 to it, but it keeps telling me : "Could not Connect to device. Try reconnecting or restarting your device". I restarted my computer and my phone a couple of times and still the application did not work. I also tried reconnecting my device with my USB cable, but still nothing. Can anyone help me work Android File Transfer so I can transfer my music from my Mac to my Samesung Galaxy S6?