The 30-day free trial of the Organizer is fully functional, and as Rebekahy said, your data is not deleted at the end of the trial. If you subscribe, you can pick up right where you left off.
You can add your students by going to the “Account” link in the upper right corner. That will take you to a page with several options. Click the one called “Student Information” to go to the page where you add more students.