To register a 3rd party plugin for the CKEditor toolbar, first download the plugin to a web server accessible folder locally. Then invoke the 'Add Plugin' dialog and provide the name and the server relative path to the plugin file.
After saving, you will need to Add the plugin to the CKEditor toolbar.
Related Links
You can download PDF versions of the Content Contributor's, Administrator's, and Elements Reference documents from the support section of paperthin.com (requires login).
For technical support: