Sign into google and go to Maps.
Click on "My Maps". If you have no maps created yet, you will be presented with this page. click on Get Started.
An Untitled map will appear.
Click on "Import"
The following "Import KML" dialog box appears.
Copy and paste the following link into the 2'nd box below:
http://sites.google.com/site/travelmapicon/home/kml-files/markersblueflags1-25.kmz?attredirects=0&d=1
More links are here
(This and other KMZ links are referenced at the top of this page)
After pasting, occasionally you need to click somewhere outside the box for the "Upload" button to become active.
Click on "Upload from URL" and you will see something like the following.
It automatically renames "Untitled" in the Title box to the name of the file you just imported.
Click on "Done" and then click "My Maps" and you will see the new map under "Created by me"
You now have this group of custom markers when you make your own maps.
The custom icons in this map will be available to use in other maps "custom icons" as long as this map is available.
Click on OK, then click on "Done"
You can click on "My Maps" again to see a list of maps created.
Notice that down at the bottom left hand corner "new map for someone" is checked.
Only the standard google map icons are available for use with the new map you just created.
But if you click on the "markers blue flags 1-25" under "Created by me",
it will join the "new map for someone" down in the bottom left corner.
So now you can use the custom blue flag numbered icons with the "new map for someone" and any other map you add under "hide". All maps clicked on under "My Maps" that appear under "Hide" can share icons with the other maps under "Hide".
These custom blue flag markers you imported with "markers blue flag 1-25" can be used with a new map you create anytime in the future just by selecting it from "My Maps". Import other groups of icons and save them to their own map. Select from one or more groups depending on your needs.
The icons contained in these imported maps will appear under "My icons" in your new map.
You can uncheck the box next to "markers blue flag 1-25" under "hide". Those markers no longer show on the active map to the right,
but the custom icons are still available for use.
Now click on "new map for someone" and zoom out until you see the blue marker over Kansas for that map.
Click on "Edit"
Then click on the blue placemark itself
In the dialog box next to "Title" give it a name like "new placemark"
Then click on the blue marker icon to the right of the "Title" dialog box on the map
It will present you with alternate default icons. When you click on "My icons" you will then see all the new numbered flag icons shared from the imported map KMZ map.
Choose an icon from My icons
These and any other custom icons you import with KMZ files will appear in you "My icons" just by clicking on the the imported map icons in My Maps.
Here is a video which makes it easier to follow along
http://www.youtube.com/watch?v=oZFzZ42eI0s
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View dark blue flags 1-50.kmz in a larger map
click on view "dark blue flags 1-50.kmz" and "save to my maps" when signed into google maps.
They will appear in your custom icons - "My icons"
View fat yellow a-z.kmz in a larger map