Currently, there is not a way to change the program to "require registration" or vice versa after it has already been created. 

If no tickets have been sold to any events under the program:
  1. From under Tickets > Program search > Select the Program
  2. Under Tasks, click Delete program.
  3. Go to Tickets > Click Add Scheduled Program, and add the program again.
If tickets have already been purchased for program events:
  1. Refund all tickets sold to the program.  For patrons that paid with credit card, you may want to refund to  an other payment method to ensure their credit card does not get refunded.
  2. Mark the program as inactive (and change it to a name such as "DO NOT USE - INACTIVE PROGRAM")
  3. Add the program again and check the "Requires registration" box when creating it
  4. Re-enter the sales orders.  Again, you can reenter the sales orders with the Other payment method.