Should I enter 1098-T form if my parents already claimed on their tax forms?

No.  If you are being claimed as a dependent on your parent's tax return, the Form 1098-T is entered on their tax return.

You may need to enter the Form 1098-T on your tax return if you had scholarship income, as reported in box 5, that was more than the qualifying education expenses, listed in box 1, on your 1098-T form. In that case, you may have taxable income that would need to be reflected on your tax return.