To add radio buttons to a TDBRadioGroup, edit the Items property in the Object Inspector. Each string in Items makes a radio button appear in the group box with the string as its caption.  
 
When the user selects a radio button, the “value” of the selected button becomes the contents of the linked field for the current record in the dataset. Specify values for the buttons by editing the Values property in the Object Inspector; the first string in Values corresponds to the first string in Items, and so forth. If no Values strings are set, each button’s caption serves as its value.