USB Drive on Airport Extreme

Hi. My english is not so good, but I’ll give my best.
I’ve a USB drive (HFS+) mounted on an Airport Extreme and in it a folder with all my uncompressed music. Can I access that folder from roon? I’ve already seen that I’ve to use smb, but I don’t know how…
I’m running roon on a MacBook Pro with El Capitan
Thanks a lot