If you have Solasta via Steam, click Dungeon Maker on the main Solasta menu, then click the Browse Workshop button at the bottom. You will browse the Steam workshop and click the Subscribe button to download and install a dungeon module. I believe you will have to restart Solasta to see the new module, either under Campaigns tab or Locations tab in the Dungeon Maker screen. Some of them are quite good and challenging, though they don't have the world map travel/random encounter features (yet! Fingers crossed they will be able to add these to the Dungeon Maker some day!).