amend a return for deceased sister

   My sister died earlier in 2021 and I am the executor of her estate. While reviewing her papers I discovered that she did not report royalties from a lease on her 2019 Federal return. I want to use TT to amend this return, but do not know what forms, etc. are necessary.  

   I will also need to file her Federal and State returns both for 2020 (she was too ill to complete them earlier this year) and for 2021. Will I need the same forms or will there be additional ones I must use?