Next, visit the page of a Plaze. Here’s the one for my office, for example. Now click the “Make Landmark” bookmark on your toolbar: after a brief pause you’ll be prompted to save a file.
Save this file and copy it to your Nokia Maps-enabled mobile, and open it. You’ll now be able to save the location and details of the Plaze as a landmark, which you can then use just like any other landmark in Nokia Maps. I’ve prepared a brief how-to screencast that illustrates all the steps: