I filed single and need to amend my return for 2020. The IRS has already accepted my return and sent me the money, but I can’t find a way to amend my return. How can I?

There is no doc saved on my account for me to go in and amend, but if I hit continue with return all my info is there. Do I just go in and fix that, or is there a specific way to amend my 2020 return that has been accepted?