Hi Frank,
When you are on the properties panel for your multiple choice question, you should see a Data Source option on the right hand side. If you click that, you'll get a pop-up where you select the Data Source you want to connect to. At the bottom of the pop-up you can also select a Filter for your Data Source.
The two drop downs below will be populated with the information from your chosen Data Source. You can pick a column to display to the end user in your multiple choice question, as well as a column to be returned as a usable value (once the question has been added to the parser). An example where you'd have two different values would be if you wanted to display a name, but have the email address as a value.
Hopefully that helps, let us know if you have any problems!