You must complete the FAFSA to be eligible for some forms of student aid. Directions are available at: http://sfa.osu.edu/.
The Student Service Center can assist you with this and other financial aid questions: http://www.scsc.osu.edu/. You can also review the chart at: http://sfa.osu.edu/howtokeepit/index.asp?tab=h#pagecontent.
You will need to contact the Student Service Center (ssc.osu.edu, 614-292-0300) about your options for re-adding the classes. Please note that if you plan to continue in the course, you should prioritize getting them added to your schedule. You will need to add back all of the classes that you were scheduled for at the time you were dropped and will be given a limited window in which to pay for the courses. If you have been dropped for non-payment in the past, the SSC can walk you through your options.