Since when did the Kobayashi Maru appear in ENT?
It's from the ENT novels, not any TV episode.
STAR TREK: ENTERPRISE — KOBAYASHI MARU
The exciting follow-up to Star Trek: Enterprise—The Good That Men Do describes the incident that sparked the start of the Romulan War: the destruction of the merchant ship Kobayashi Maru.
The fragile Collation of Planets is convinced that in order to hold the fledgling alliance together something must be done to stop the random destruction of civilian shipping. Under orders from Starfleet, Captain Jonathan Archer and Captain Erica Hernandez, commanders of two of the most powerful starships, have been reduced to convey duty, no more than glorified babysitting. Both captains know that there is something behind all of this systemic destruction. Captain Archer believes he knows who—the Romulans. But will anyone listen to him before it is too late?