To install the plugin, simply in Eclipse use the update site:
http://keytool.sourceforge.net/update
This is done through Help - Software Updates - Find and install - Search for new feature....
Click New Remote Site and add http://keytool.sourceforge.net/update in name and URL, and
make sure its checked.
Hit Finish.
It's also possible to download it as a zip-file or as an selfcontained application.