The "insert your own key name here" part of this should be the exact file name of the saved mission (the actual file name, not the mission name set up in the Intel section of the editor.
So for example if your mission is titled "Operation Bitchslap" and you save it as "112010OA061RC.Desert_E" (or whatever you consistently save your file names as), the description file part should have the following:
doneKeys[]={112010OA061RC};
And when the mission completes, you would have the following (I usually put it at the end of my outro.sqf):
activateKey "112010OA061RC";