I completed the penalty waiver request online but need to correct an amount in it. I can't get back to the waiver section on turbo tax. Any advice?

Yes, you can reopen the waivers section in TurboTax Online and correct the entries you made when requesting a waiver. This is assuming you've not filed- if you already filed, you will need to amend.  See How to File an Amended Tax Return with the IRS if necessary.

Here's how:

• Navigate to the magnifying glass in the upper right of your screen, type "underpayment penalty" then choose the first option, "Jump to underpayment penalty."
• Continue through the interview screens until you arrive at the section that says "You Can Request a Waiver." Choose yes, you would like to request a waiver of your penalty.
• Proceed and make the corrections.