The preparation of Form 1040X Amended Return is expected to become available late on Feb 25 or morning of Feb 26. It will hopefully be in this week's routine update which often occurs overnight early Thursday morning.
In the meantime, do NOT make any changes in your return. When you start the amending process, it has to start off exactly as originally filed.
If you were due a Federal refund, you should wait for your original return to fully process at the IRS and that you have received the refund. Before you prepare your amended return, also see the info in this FAQ and video:
FAQ: How do I amend my Federal tax return for this current year?
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-federal-tax-return-curr...
If you amend the Federal return, you may also have to amend the state return (if applicable.)