You cannot prepare aa amended 2023 return using online. You need to use the downloaded desktop software on a full PC or Mac.
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-already-filed/L4VjJ9BA2_US_en_US?uid=m76mq6z2
Do not expect quick results from amending. It can take four months or more for the IRS to process an amended return.
You can watch for information here:
https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1
AND, even with the desktop software...at this late date, a 2023 amended tax return would have to be printed, signed, dated, and filed by you at the Post Office.