You cannot change or add anything on the return that you just e-filed. It is too late, just like when you put an envelope in a US mailbox.
It will say Pending until the IRS either accepts or rejects your return which won't be until after they open on Feb 12, 2021, see
https://www.irs.gov/newsroom/2021-tax-filing-season-begins-feb-12-irs-outlines-steps-to-speed-refund...
