Tax return was accepted but needs to be amended

Do NOT try to amend your tax return until it has been fully processed.  If you send in an amended return before the IRS processes the return you will just cause confusion and delays.  WAIT until the return has been processed completely and then you can amend it by preparing a Form 1040X which must be printed, signed and mailed.  Amended returns cannot be e-filed.

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed?jump_to=answer_3288565

A 1040X cannot be e-filed.  It must be printed and mailed.  It will take about 3-4 months for the IRS to process an amended return.  It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.

Wait about 3 weeks from mailing and you can check the status of your amended return:

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1

https://www.irs.gov/filing/individuals/amended-returns-form-1040-x/amended-return-frequently-asked-questions

https://ttlc.intuit.com/questions/1908543-do-i-need-to-amend

https://ttlc.intuit.com/questions/2566895-what-does-it-mean-to-amend-a-return