The 1040X used to amend your tax return isn’t available yet but should be ready by the end of next week.
You won't be able to file an amendment until your tax return is fully processed and you receive your refund or your balance due is deducted from your account.
Refer to the TurboTax articles: Amending Your Income Tax Return and How to Correct Federal Tax Returns for additional information.
Once you file your amendment, you can check the status of your amended tax return at Where’s My Amended Return?