For this year or next year? Did you file a return yet for this year? If not, then all you will need to do is create an account online and walk through the steps of answering the questions and entering the forms. TurboTax will calculate what you owe then.
You can use the TurboTax Tax Caster to determine how much you will owe for next year.
If this is a retirement plan early withdrawal you will likely be subject to a 10% penalty unless you meet one of the exceptions to the penalty.