how do I enter a roth conversion

If you are being penalized 6%, you most likely mistakenly entered the amount of the conversion as a Roth IRA contribution.  

Revisit the Deductions and Credits > Retirement and Investments > Traditional and Roth IRA Contributions section of your return and remove any Roth IRA contributions that you entered that are related to the amount that was converted.  

If you did make a separate contribution to your Roth IRA other than what was converted, then pay attention to the messages on the screen because you may not be eligible to make a Roth IRA contribution and that is what is causing the penalty.  

The only thing you need to do in your return to report that a distribution reported on Form 1099-R was converted to a Roth IRA is to enter the Form 1099-R and answer all of the follow-up questions.  

(You did not say that you are doing a backdoor Roth IRA conversion, but if that is the case, you will also need to be sure that you have reported the non-deductible contribution made to your Traditional IRA which was later converted to the Roth.)