I need to amend my 2020 tax return to add my dependent

@ftbragg81 - then you need to file the amendment as you stated; what is your question? ... Can you explain why you didn't add the dependent originally - might be able to save you some time if you explained more. 

I filed as head of household, but neglected to add my offspring's name and SSN as my dependent.

Do I have to re-enter my entire tax info to create an amended return?

How to Amend

https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...