How do I put down spas and diners and how do they work?

You have go to manage worlds and click on the lot you want to place it on. Select build mode icon to enter the lot and change the lot designation from residential ( or whatever ) to spa, cafe, restaurant or anything else on the drop down list. Then ( while still on the lot ) open the gallery and select which buildind you want and place it. After that you can edit the menu, dress code and uniforms.