INSTALLATION:
FIRST STEP, you must Remove ALL default "ckeditor" files:
1 - Go to: ../admin/view/javascript/. and manually delete the OLD "ckeditor" folder completely.
SECOND STEP, Install the new files:
2 - Unzip the downloaded file in the folder of your choice.
3 - Go to: ../admin/view/javascript/. and manually upload the NEW "ckeditor" folder.
4 - In admin, check that CKeditor loads correctly (open Catalog > Categories for example).
5 - ... you might have to press "CTRL-F5" once or twice, to refresh your browser's cache.