Tutorial is up to date with r011.
To attract creatures to your dungeon, you need to offer at least a space for lairs, and some food. Food comes from farmland currently, and creatures are vegetarians so far, so that will work.
The start map already has a lair for some creatures, so you don’t need to take care of that. But you need space for farmland.
Imps will excavate new corridors and rooms for you. Click on a wall next to an existing room or corridor. A mining mark will appear there and an imp will come to clear that square of earth, and floor it (sometimes another imp will come for flooring). This way you can create new rooms and corridors.
So, to create a farm, let the imps dig out a 3×3 area, then press the „food“ button and then click the floors of the new area. They should turn into grassland. In r011 and older, plants will start growing there automatically.
After you’re done with the farm, press the right mouse button to revert the command tool to „mark for digging“.
Once you have lair space and a farm, creatures will start to join your dungeon.
Tip: Don’t build any other rooms until the powersnails have planted enough crops in your farm. They won’t work if they are hungry, and if nothing is growing, they can’t eat anything. Also make sure to have at least a 3×3 farm to start with.