Question about Pioneer SPH-20DAB

You can't, you have to use Apps from your mobile phone's navigation system.
What you can try is to buy the TomTom app and install it on your mobile phone. Maybe it will work afterwards. But I am not sure .

I always connect my smartphone to Google Maps, I don't think it works any other way.

Not as far as I know, as this radio runs entirely via smartphone. So the most you can do is install tomtom on your mobile.