Add an option group control to the form. The wizard will walk you through the process. You can choose radio buttons as the graphic choice and enter the values for your four buttons. When referencing the control, you would reference the option group, never any of the radio buttons. The option group is the control that will be bound to your table.
Although it is possible to add radio buttons directly on the form, they will not work in concert as they do when controlled by an option group.