I received a 1099-G for Oregon state refund. How do I find "Total of all your payments and withholding"? The form I received is simple and only has "Total Tax Refunds".

If this in reference to the 2017 state refund (received in 2018) and whether it is taxable on your 2018 tax year return, "Total of all your payments and withholding" means the state tax you claimed on your 2017 Federal return. 

You can find this number on your 2017 Schedule A line 5a.

If you itemized on your 2017 Federal Tax return, and you took a credit for state income tax paid, you now must claim (at least part) of that refunded state tax as income. The program will ask the questions needed for the calculation of the taxable portion. 

If you took the Standard Deduction on your 2017 return, the refund is not reported as income (and you won't have a 2017 Schedule A).

If you did itemized on your 2017 return, but you claimed sales tax rather than income tax paid (5b), the refund is not claimed as income. 

Thank you for the clarification, it answered my question!

I have a follow up question. I also received a 1099-G state refund document from a prior year, specifically the document states "Refunds for Tax Year 2016". How do I handle entering this information through the TurboTax Desktop SW? Do I enter 2016 Schedule A line 5a for the section "Total of all your payments and withholding" or is this handled differently?

Yes, use the amount of tax you claimed as a deduction on your 2016 return for the 2016 tax year refund.