To do a manual install of a plugin:
- Download the plugin file.
- Open calibre and then the main preferences.
- At the bottom, click on plugins.
- Click the "Load plugin from file" button.
- Find and select the downloaded plugin file and press OK.
- Answer yes or OK for the prompt about installing the plugin and the restart calibre.
Once calibre has restarted, I suggest you check the configuration before connecting the device. If there are any problems, delete the configuration file as I suggested above.