I am working on my tax with turbotax. but I want to redo the penalty for the federal tax. How do I get back on the turbotax to recalculate?

If you have not filed your return, you can make changes:

Log in to your TurboTax Online Account

From the Overview page

Click on My TurboTax

My Tax Timeline

In the Some things you can do area

Select Add a state

This will let you back into your Return to complete and File it.

If you have already filed the return, you will not be able to make changes to it.  You will have to amend it.  Do not amend until you have determined if the IRS accepted or rejected the return.  If accepted wait until either you have received your refund or any payment you have made to the IRS has cleared.  If rejected you may go ahead and make the needed changes (do not amend).  

You will be able to amend as soon as Form 1040X becomes available.  At this time the expected date of availability for the form 1040X is

02/27/2020 , however that date is subject to change.  You can track it's availability by going to the following link.

https://care-cdn.prodsupportsite.a.intuit.com/forms-availability/turbotax_fed_online_individual.html

Do I need to amend?

How do I amend my 2019 TurboTax Online return?