I've seen a number of posts complaining that the owner's manual does not cover this topic very well or at all.

You may find what I've discovered useful:

Touch screen:

Tap City

There is an area labeled 'Ptcd' bottom left

Tap that and you have a screen to enter your postcode

Voice control:

Say 'Navigation'

Say 'Enter Post code'

Say the destination post code

Note that when the screen is displayed after saying 'Navigation' there is a an area with 'Enter address' etc shown.

If you tap this and scroll down, there is a whole list of help giving acceptable voice commands.  The key is to use the prefix 'Enter'.

So yes the manual is useless but there is in-car help available

Pretty impressive once you know how it works

Hope this helps

Good luck

You lives and learns!  I never knew how to do it with voice control.  Thanks a lot.