You should have received a tax form from the pension, probably 1099R. Jut go to the section in TurboTax that askes if you received this form, and fill in the amounts from each box on the form (Taxable, non-taxable, etc.). If you contributed to the pension, that amount is tax-free. If the form has this wrong, you need to get your contribution from the pension or your records. The taxable portion is treated as ordinary interest and will probably goe right to page 1, line 16b of Form 1040, and there is no other form that will result in a lower tax.
