This plugin replaces the plain multiline text field on BP forums by a CKEditor.
After you have correctly installed this plugin and visited its Settings page, you will need to specify where are located (path and URL) your copies of CKEditor and, optionally, CKFinder. The plugin has a build-in copy of CKEditor just in case you do not provide one.
If after you save those paths the plugin tells you that the files ckeditor.php or ckfinder.php can't be readed from the specified locations, please verify that the path is correct, that the folder is readable and that the copy of CKEditor has all its files.
Below the General Settings is the Editor Settings. Once the plugin has recognized the copies of CKEditor/CKFinder you can define almost every parameters exposed by CKEditor. Please refer to its documentation for support about those parameters.