I am a student and I am using the free Tax Cut software from Turbo tax to prepare my taxes. I realized I can claim deductions for the amount I paid for registration of cars. How do I add this to my return? I have never made adjustments to my old returns. Is there a special form I can download from somewhere? How can I estimate if I will get any money back from previous years filing now?

Do you itemize all your deductions on your taxes? If you take the standard deduction you can't just cherry pick what you want to "add" to your standard deduction.

Only property tax and sales tax is deductible. This deduction is itemized deduction. You will take deduction only if your itemized deductions are more than your standard deduction. Read: Your U.S. Tax Return: Itemized Deductions