Solo adventures of Hearthstone had always been available to download for old gamers. The last rotation changed things on this level since the Icecrown's Citadel and the Kobolds & Catacombs Adventure have seen their rewards getting out of the Classic mode.
If you are a new player on Hearthstone and you create a new Battle.net account, you wouldn't even have had the offer of downloading those adventures. From now on, you simply have to get them back and download them for free here.
Remember that the other adventures with chapters which have to be paid for can only be unlocked with in-game gold coins.
Written by Jérémie "Djey" Mathis. Translated from French by Millenium.us.org.