This addon is a plugin. You need to extract it to your /plugins folder to install it.
FCKeditor is a popular WYSIWYG toolbar for your comment forms and posts. Includes Source editing, smileys and Youtube/Google/Soapbox/Vimeo/Revver/Dailymotion/VideoJug/MetaCafe video embedding
Not compatible with Safari.
You can enable other formatters (not tinymce or dojo editor) before FCKeditor. The user can decide whether he/she wants the FCKeditor toolbar or not. If yes they can enable it via Account Tab->Forum Preferences. If no then any other formatter you have chosen will be used. This is for forum where certain members prefer a toolbar while others might prefer BBCode. So now u can give them the choice.
You can enable FCKeditor for all members when you install the extension Support this extension