You should have received a 1099-G form from your State.
If you received a refund of state or local income taxes from last year's tax return, you may receive a Form 1099-G reporting this refund as income. If you itemized deductions on your federal return in the same year that you received the state or local refund, the refund may be considered taxable income.
None of your refund is taxable if, (a) did not itemize your deductions, or (b) elected to deduct state and local general sales taxes instead of state and local income taxes. Then you would not have to enter any refund received from your State.