My federal return was accepted and I need to amend it, but there is no "amend return" on the 2020 tax return under "Your tax returns and documents" .. It only shows it for 2019, 2018, 2017 etc.
Does my state return need to be accepted too to amend?
Slow down. You cannot amend a tax return that was just accepted. You have to wait for it to be processed by the IRS.
Do not try to change anything on your return now. You have to wait. Once your return has been processed you will complete a Form 1040X --- which is not yet available --- and submit it to amend the mistakes made when you filed your original return. It takes the IRS at least four months to process an amended return.