Do you have to claim last year's refund to taxable income for 2020. We're is this entered if so?

Possibly.  If you itemized deductions on your Federal return in 2019 and took a State income Tax deduction, then you may have to include the state tax refund in your income for 2020.  If you took the standard deduction in 2019, you will not need to include any portion of your 2019 state tax refund at taxable income.  You can check this out by reviewing your 2019 1040 tax return on line 9.  You can also look for Schedule A with your 2019 tax return information.  If there is no Schedule A, then you took the standard deduction and do not need to include your 2019 state tax refund.

If you receive a 1099-G from your state revenue agency, your state tax refund would be reported on this form.  In TurboTax, add the 1099-G under "Other Common Income".  You can also enter "Form 1099-G" in the search box in Turbotax and will be able to jump to the 1099-G entry screens. 

You do not need to include your Federal Tax Refund as income.