Harley Davidson ipod interface

I had no problem with a iPod Shuffle but I've now bought a Nano and have trouble with the advance feature. If my Nano is hooked directly into the usb port on my 2014 FLHTK, I cannot use the advance feature. If I'm connected to the Nano via Bluetooth, I can use the left-hand thumb button to advance to the next song (in shuffle mode).

I'd like to know how to set the Nano so I can use the Boom! Audio thumb buttons to advance songs when the iPod is connected to the usb port.

Yes, you should be listening to the screaming eagle pipes not an ipod!