The installation process is not as easy as with most other plugins, but i think it shouldn't be too hard using this list:
- Download the complete package
- Extract the package using any programm you want (i.e.: 7zip)
- Upload the extracted folder, including all subfolders (no matter if empty or not) to the plugin directory of your wordpress installation (/wp-content/plugins/)
- Activate the plugin in your wordpress administration center
- If necessary (script will tell you), create the folder "img" as subdirectory of the wpmathpublisher directory and set it to chmod 777
- Done. Go for it!