Check out the points 1 & 2 on the post from WebDevDan on this thread CX-3 Apple CarPlay/Android Auto retrofit. It summarises the situation better than I could.
Note - I'm led to believe that if you have got a correct hub unit with the phone icon against one of the USB slots and it was installed before the infotainment was updated to version 74.00.32A (or maybe an earlier 70.xx.xxx or later version had been installed?), then it won't work and you'll need search this site for potential information.