Attached is a simple project that illustrates a very simple master-detail TDBF setup.
Most of the settings are done explicitly in code rather than using the Object Inspector, so you can see the important properties and indexes that need to be set up. Otherwise these settings may be overlooked in the Object Inspector (or are more hidden in the form's .lfm file).
Best practice is to use a datamodule to contain your data objects and files, but that is omitted from this example for simplicity.