How to find portal menu:Theme Editor

Hi, friends:

  My portal version is 7.4,  the user is with authorization group :administrators,  but I can not find  "System Administration --> Portal Display ---> Theme Editor"

the under menu of "System Administration --> Portal Display"  as below picture.

Image may be NSFW.
Clik here to view.

Please tell me how to find "Theme Editor"

Thanks

Jesse.