How do you get the editor

[[DnC]]

Rightmouse click on the RTW shortcut and choose properties. Add -enable_editor behind "G:\Rome - Total War\RomeTW.exe", like this; "G:\Rome - Total War\RomeTW.exe" -enable_editor.
Note that this is where my game is installed, yours will mostlikely be installed elsewhere, so don't copy the entire line, just -enable_editor. Beware, there needs to be a space between "G:\Rome - Total War\RomeTW.exe" and -enable_editor.

Edit: PS. You can find the editor under the options menu. It will be added at the bottom and be called Battle Editor.