WordPress.org

The installation process is not as easy as with most other plugins, but i think it shouldn't be too hard using this list:

1. Download the complete package
2. Extract the package using any programm you want (i.e.: 7zip)
3. Upload the extracted folder, including all subfolders (no matter if empty or not) to the plugin directory of your wordpress installation (/wp-content/plugins/)
4. Activate the plugin in your wordpress administration center
5. If necessary (script will tell you), create the folder "img" as subdirectory of the wpmathpublisher directory and set it to chmod 777
6. Done. Go for it!