Since you are posting from a "Live" version  you can arrange for the Live help you are paying the extra fee for with your questions from  5 a.m. to 5 p.m. Pacific time Monday - Friday.

https://ttlc.intuit.com/questions/4124827-how-do-i-connect-with-a-tax-expert-in-turbotax-live

Select a tax year for specific amending instructions.

Keep in mind: You have 3 years from the date you filed your return (or 2 years after you paid the tax due, whichever is later) to file an amended return, which means you don't have to get it done by the April 15 filing deadline.

• 2018
• 2017
• 2016

You need to log in to the account you used for that year.  If you need to amend 2017 or prior you need to download the .tax file and use the Desktop amend program.  You can amend 2018 online.

That's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
https://myturbotax.intuit.com/account-recovery/

If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.