By aux port do you mean the one on the front of the radio or the one next to the power outlet. I use the one next to the power outlet to connect a usb stick, it just needs an adaptor cable (mentioned in the handbook). I got my cable from ebay for https://www.ebay.co.uk/itm/173090249727. I have no connection with the vendor or ebay , just a satisfied customer.
Edit I have a late 2014 (64 plate) ES spec.