Businesses in your town need to be loaded with goods in order to start working. You can see the amount of goods you currently have at the top of your screen.
Tap a business building with a 'ZzZ' icon to select it and tap it again to load it with goods.
A working business will produce coins once it's finished. Tap a working building once to see how much time it will take.
Note: you can finish the production instantly using superbucks by clicking the green round button.
See the article "Collecting profits" for further details on how to collect coins from businesses.