You can install CKEditor easily by selecting an appropriate procedure (fresh installation or upgrade) by doing the following steps:
This way is used to install CKEditor for the first time.
Download the version 3.x of the editor here.
Extract (decompress) the downloaded archive to a directory called ckeditor in the root of your website.
You can place the files in any path of your website. The ckeditor directory is the default one.
Upgrading an existing CKEditor installation
Rename your old editor folder to a backup folder, for example, "ckeditor_old".
Download the version 3.x of the editor here.
Extract/Decompress the downloaded archive to the original editor directory, for example, "ckeditor".
Copy all configuration files that you have changed from the backup folder to their corresponding positions in the new directory. These files could include (but not limited to) the following files:
config.js
contents.css
plugins/templates/templates/default.js
plugins/styles/styles/default.js
plugins/pastefromword/filter/default.js