There are two methods for uploading files available in the CKEditor for Drupal module:
- by using a commercial file browser like CKFinder, an advanced Ajax file manager;
- by using modules like IMCE.
Please note that while you need to purchase CKFinder separately and manually add the files to your Drupal site, the CKEditor for Drupal module already comes with CKFinder integration built-in, so once you add the files, the configuration process is quick and easy.
To select a preferred file browser, adjust CKEditor profiles in the Administration panel > Site configuration > CKEditor section. In the File browser settings section you can choose which file browser will be used for each profile.
Please note that in order to choose an uploader module other than CKFinder, you should install an appropriate Drupal module first by yourself.