Desi, there are multiple ways to do this. How many people are on your list? If it's manageable, you can simple import the list as members; and then manually change the program status to the appropriate status. For example, if your list contains 25 people who registered - and 10 attended - you can select all members and change their program status to "registered". And then select those 10, and change their status to "attended".
Or you can build a smart campaign to define the program status based on specific data. For example, if you have a custom field called "attendee status" - where you store a standard list of status values (registered, attended, etc. as part of your list import) - when the list has been uploaded as a static list to the program, you can run the batch campaign against that list and use "choices" within the "change program status" flow step to assign the proper status.