Place four berry stems into the wreath at the north, south, east, and west area towards the back.
Next, add four more stems in between each area.
Continue adding more stems in between sections, adding them more towards the front of the wreath as you continue.
Add a few remaining stems in the bottom center if you want.
Notes
Make sure the stems are held in place by the wreath so that they do not fall out. If you think that you will not want to reuse the wreath you could add a little glue to the berry stems to permanently attach them to the wreath.