Instructions on how to Amend 2019 return from Married Filing Separate to Married Filing Joint?
https://ttlc.intuit.com/questions/1899507-how-do-i-amend-a-separate-return-to-married-filing-
Select your tax year for amending instructions:
What does it mean to "amend" a return?
· Do I Need to Amend my Tax Return?