Help text for push buttons can be entered in the Description field of the item master. The text appears in a small help window directly at the push button if the mouse pointer is put on the button.
For radio buttons you can enter help texts in the Description field of the field master or in the field Description-M of the mask-field-default relation. You enter the text for the (invisible) field which the radio button area is defined at. When the area is entered in mask-edit state, the help text will be displayed in the footer line of the mask.