How do I populate radio field choices in code that have a fixed list of options in the field definition,

How do I populate radio field choices in code that have a fixed list of options in the field definition,

I'm new to Zoho, only started working on it this week, but not new to application development for business after working for many years in Lotus Domino.
Anyway I am developing some new forms and can't find a way to populate the options for radio fields and selection fields in code rather than using a hard coded list. 
Any help you can give will be greatly appreciated as I can't find examples anywhere so far to show me how to do this.