I have a DNX890HD - your 2015 Grand Tour probably has a later model with more bells and whistles.
On my DNX890HD:
1) You save addresses by first entering the components of the address until its complete and the location recognized. Then it gives you 3 options: Routes, "i" and Go! Select the "i" and it gives you another screen with a map, the address and three horizontal bars. Touch those horizontal bars and it responds with "Save" or "Cancel". Hit "Save" and then it brings up the keyboard; hit "Done" on the keyboard, and then it says the address is added to Saved Places.
2) Cellphone contacts only get downloaded to the phone app and are not visible to the Navigation app, unfortunately, on my model.