This is how I install the WP Cumulus to my wordpress blog. This is a manual method (for whatever reason, automatic way by simply click install in my wp admin does not work)

1. goto wordpress plugin for wp cumulus at http://wordpress.org/extend/plugins/wp-cumulus/
2. click the download button at the top right
3. save it to a directory eg. e:\temp
4. unzip the content to a folder eg. e:\temp\wp-cumulus
5. login into the web hosting server and extract the folder \wp-cumulus\ to /wp-content/plugins/  (some server using /public_html/wp-content/plugins/ ) , some hosting server has it’s file manager, so you can transfer the folder
6. You may also use cuteFTP, or whatever FTP software to transfer the files.
7. After it is done, you can goto the wordpress admin, at the left panel, click on the Plugins, the wp cumulus should be listed there
8. If for whatever reason it is not found here, goto your web hosting path /wp-content/plugins/ to check if /wp-cumulus folder is there , you might even have misplace it to different folder, check /wp-content/ or / folder
9. Once you have done and can be found in the plugin list of the wordpress admin plugins, just click activate button under the plugin icon
10. click on the appearance in the wp admin panel,  under it there’s a widget, click on it
11. Here you can find the wp-cumulus widget, you can drag it to whichever position you want whether it’s a sidebar or whatever..
12. Set the size of the sphere and speed to your liking and experiment it, save and it’s done

Enjoy this really cool tag rotating sphere. I love it. Thank you so much to the creator Roy Tanck