The editor for games powered by the Doom 3 engine is included in the game exe and can be accessed (normally) in two ways;
- Start the game, drop the console and type 'editor'
- Create a new shortcut and add a few 'commands' to it.
Method two is preferable as you have more control over what happens when the editor starts. Because setting up the Quake 4 editor is functionally the same as setting up Doom 3's editor click here to read the following tutorial; "
Doom 3 - setting up the editor"
Essentially though you need to edit your desktop short cut so it's similar to the following;
"E:\\Program Files\Quake4\Quake4.exe" +r_fullscreen 0 +r_gamma 1 +vid_restart +wait +editor
If
+r_gamma doesn't work, try
r_brightness 1 to prevent the editor from over brightening your desktops gamma/brightness.