How to add a MonoDevelop editor script?

I would like to add a MonoDevelop script but I don’t know how.

I would like to add this script: http://forum.unity3d.com/threads/145027-Unity-is-overwriting-my-MonoDevelop-target-framework-setting-every-time-it-syncs

Thanks.

SOLVED!

Actually I just put the script in the Script folder but the editor script is executed with Unity. But this script can modify MonoDevelop preferences.