I missed 2024 RMD and need to file form 5329 while paying the penalty tax. How do I enter the tax on schedule 2, line 8?

You can process the form 5329 in the TurboTax desktop software. You can use the Tax Tools option on your left menu bar while you are working on your return to then bring up Tools, which will have an option to Save your return to your computer so you don't need to start your online return over in the desktop version of TurboTax.

In the desktop TurboTax product, use the Forms menu option to bring up Form 5329. Scroll down to Part IX, line 52 and enter your required minimum distribution amount. Enter the amount of any RMD you took in line 53. Use the Waiver of Tax Smart Worksheet below line 53 to enter the amount you want to exclude from tax, and click on the Explain box to enter an explanation of why you missed making the distribution. You won't have to pay the tax for not taking your RMD on your return, pending a determination from the IRS later on.