I do not think that importing iTunes music to Amazon is the best way for me. Too much work and hassle. I did import the free 250 tracks to see that it works a few years ago, and it did. But since ALL my music in iTunes program is DRM-free, I have no problems with any device playing my music. I copied my iTunes Media folder to my NAS, and even other drives and I can access it via DLNA apps.
All I do is access my iTunes music source and Bluetooth it to the Echo. My favorite way to do this is to use the free Avia app on my Android tablet and access my NAS where all 17,000 music tracks are stored, select one of the many playlists I have, and send audio from tablet to Echo via Bluetooth. Easy!