I'd probably use radio buttons but it's all the same basic process.
Select Manage | Value Lists and click New to start a new Value List.
Use the Custom Values option to type in your two values:
Click Ok until you have the dialog boxes closed.
On your layout, select a text field while in layout mode and use the Inspector's data tab to change the field format from Edit Box to drop down list. When you do so, a drop down for selecting which value list will appear and you can select your new custom values value list.
The steps are the same for radio buttons, check boxes or a pop up menu as well as a drop down list, the only difference is the format option you select instead of Edit Box for your field.