How can I specify additional details that must be provided while creating a program?

If you want to create custom fields to capture additional program details, you must get them deployed for your organization, so they are available in both the user interface and the Project Program REST API.

For example, if you want program managers in your organization to capture the name of the business unit associated with a program, ask your Projects administrator to deploy Business Unit as an additional field in the Create Program interface. Once this field is deployed, it will be available in the user interface as well as in the Project Program REST API, and program managers will be able to capture this detail when they create a program.