As has already been mentioned several times, The Color of Madness DLC expansion set for Darkest Dungeon has introduced a completely new location to the game - Farmstead. With it, a new gameplay mode has been added - The Endless Harvest - where the player's task is simply to survive, and after killing a group of enemies, another appears and the battle continues until the player escapes or the team is beaten.
Unlike the Courtyard from the previous expansion, The Crimson Curse, where special invitations were required, entering Farmstead is incredibly simple. You just have to wait a few weeks after the start of the game (completing a few missions) for the new crystal icon representing this zone to appear on the mission selection screen. At first, you have to play two short missions and beat one of the new bosses, The Miller. After their completion, Farmstead will have the opportunity to activate the expedition to the aforementioned The Eternal Harvest.
Note - remember that the Eternal Harvest expedition does not involve time spent in the game. If you start it during the 20th week, it will also be 20 weeks after the end of the week. It gives you the possibility to send teams for additional missions, but remember that one day you will have to send them for a normal mission - make sure there is someone to send.