First, turn off your editor (JCE Editor Mambot).

• In the administration panel, Go to Site >Global Configuration.  Click in the site tab.
• Go to the Default WYSIWYG Editor: Choose  No WYSIWYG Editor from the drop down menu.
• Click the Save Button.

Copy the Java Script that you wish to insert into your content item.

Go to the content item or create a content item that you want the Java Script in.

Paste the Java Script into the item.

Click the Save button.

From Site > Global Configuration, turn the WYSIWYG Editor back on.

WARNING:  Whenever editing that particular content item, first disable the WYSIWYG Editor.