Currently, Map+ only supports addresses within the United States (sorry).
Getting Started:
After installing Map+ and restarting Firefox, click on the "Tools" menu
and select "Add-ons." A dialog box will appear with a list of installed
Add-ons, click on the Map+ entry and push the "Options" button. A new
dialog box will appear. Here you can enter your address and adjust the
size of Map+. Push the "OK" button and close the Add-ons dialog. You're
all done!
As an example, highlight the following address: 1600 Amphitheatre
Parkway Mountain View, CA 94043 (hold down the left mouse button and
drag across the entire address). Now right click on this highlighted
text and you'll see a menu entry that says "View map of 1600
Amphtitheatre...". Click on that menu item and a popup with a map of
that location should appear. If you want to get directions to that
location, simply click on the little bubble icon that appears on the
map and click the "To here" link. A new tab will open with the Yahoo
driving directions.
A video of how to install and use the Map+ add-on can be found on YouTube: http://www.youtube.com/watch?v=gLIVKbYcH4Q.