IMHO, it's safest to add a folder in Conquests\Scenarios for your mod (additional units; whatever) and stick them in there -- just follow the layout of sub-directories in the Conquests (which are in Conquests\Conquests -- go figure) and recapitulate that structure in Conquests\Scenarios\MyStuff, then just add "MyStuff" to the Scenario pathing on the Scenario tab.
-- Simple as always, hm??
-Oz