How do I install an extension?
To install an extension. First download the .xml file that is the extension and then put it into extensions directory inside the Map Editor installation directory (default is C:\Program Files\Remere's Map Editor).
How do I make my own extension?
Copy the sample.xml file in the extensions folder and rename it to whatever you want. You can then modify this file to include your own, custom brushes, it will be loaded automatically by the editor.