Ditto 2.1+ (the latest version for Evolution) is part of the standard Evo 1.0.2 package, so it should have been installed with the rest of MODx.
If you chose not to install any snippets, you can get Ditto from the Extras section of the modxcms site: download of Evolution version is at
http://modxcms.com/extras/download/146/146. It may be easier to do an upgrade install of MODx with snippets included.
KP
