“Full access to DLC game packs—new zones, quests, dungeons, and more
Includes Orsinium, Thieves Guild, Dark Brotherhood, Shadows of the Hist, Morrowind (zone and story), Horns of the Reach, Clockwork City, Dragon Bones, Summerset (zone and story), Wolfhunter, Murkmire, Wrathstone, Elsweyr (zone and story), Scalebreaker, Dragonhold, Harrowstorm, and Stonethorn (our most-recent DLC!)”
To give it a spin, you just need to log into the game and pick the “free trial” option out of the cash shop. You will not pick up the currency stipend that subbers normally get, do note, and you do need to own some version of the game to take advantage of the promo.