I would like to use Turbotax to estimate my taxes for 2019. How do I do that ?

[DoninGA]

If using the TurboTax desktop editions for tax year 2018 access Forms mode by clicking on Forms.  Then click on Open Form in the upper right of the screen.  Type in what-if.  Click on the result to open the What-If Worksheet and then use 2019 tax rates on the worksheet.

Otherwise use the TurboTax calculator TaxCaster to estimate tax owed or a tax refund - https://turbotax.intuit.com/tax-tools/calculators/taxcaster/