WordPress MU

In the Design panel, I only have this subpanels:
Themes
Widgets

Why I don't have Theme editor and file editor?

...because it's a security risk to let your users edit theme files directly.

I don't understand, because I can only enter to the cpanel, and what do i do to edit the themes?

If you want to edit a theme, you will have to download whatever file you want to edit via FTP, make your changes, then upload via http://FTP...

If your users can edit the theme, it affects everyone else using that theme. they can royally screw it up or place really bad code in there.

*whisper* google userthemes. or check wpmudev. but the theme editor is having some issues with this latest upgrade, so take care.