After you file

I efiled my 2020 tax return with another program (not Turbotax) it and was accepted. I want to efile a 1040x with turbotax. I have input all the information for the 2020 return. Turbotax will not let me amend because it says I have not filed yet. But I did with another program. How do I get to 1040x on Turbotax?