When a Hatchimal is assigned to a house the house will start generating coins and you'll see your Hatchimal walking around Hatchtopia.

Assigning a Hatchimal to a house:
  • Place a house in your world and wait for it to complete construction.
  • Tap on the house.
  • Tap on the pink 'Assign' button.
  • The Collection panel will appear at the bottom of the screen.
  • Drag the chosen Hatchimal to the chosen house.
If you want to change the assigned Hatchimal, drag a new Hatchimal in its place.