On my Iowa personal tax return how do I enter a tax payment already paid by a partnership?

You can do your Iowa personal tax return using TurboTax. A tax paid by the partnership and deducted on the partnership tax return would not be entered by you on your Iowa tax return. Your K-1 schedule would reflect your share of partnership income so the tax deduction would be reflected in that number.

If you mean the partnership paid a state tax that will be reflected somehow on your Iowa tax return, then that would be an estimated tax payment and you can enter it in TurboTax in the Estimates and Other Taxes Paid section, then Estimates. You will find that in the Deductions and Credits section of TurboTax.