Can anyone help me backup my iTunes music to a Seagate Hard Drive please?

So I just bought a Seagate hard drive so I can backup my iTunes music and I just went to try it out and it won’t let me transfer my iTunes Media to my hard drive. My MacBook Pro recognizes the Seagate hard drive but I can’t transfer my iTunes Media over to it for some reason. What’s the easiest way I can transfer my iTunes Media/music to my Seagate Hard Drive?