if you need to add checkboxes to the form you can choose the Multi Selection Field. In this way, the options are showed as checkboxes and the user can select many values from multiple options.
If you want the user selects only one checkbox, you can add the "Checked Items" Validation Rule with Item Count=1 and Predicate=Exactly. Alternatively, to allow the choice of only one option you can use the Selection Field. It is displayed as select menu (default) and it can be rendered as radio button, by changing the "Selection fields rendering" Field Layout parameter. To change the parameter:
- select the Entry Unit in the Grid and in the Outline View, expand the Entry Unit and choose the Selection Field.
- in the Properties View, open the Layout Parameters dialog of the Field Layout property.
- change the "Selection fields rendering" parameter to "radio".