Apple – Support – Discussions – copy address to letter–how? ….  Easy.  baltwo has the steps below.

Copying addresses as mailing labels
You can copy an address as a mailing label and paste it into other applications.
To copy an address for a mailing label:
1. Make sure you aren’t in edit mode (the Edit button is not highlighted in blue).
2. Click (and hold) the label of the address field (such as “work” or “home”) and choose Copy Mailing Label from the pop-up menu.

Then, open the Word document and CMD+V.