If you have already submitted your return, you cannot make any changes to your tax return.
You have two options:
If your return got rejected for any reasons, you can return to the program/account to add the Form 1099B along with other changes. You do not need an amendment 1040-X.
If your return has been accepted, please see the following :
You will have to amend your return by filing a Form 1040X. You should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared.
Amended returns do not “catch up” to your original return and replace them; they are processed as two separate returns.
Amended returns have to be printed and filed by mail. It can take the IRS up to 12 weeks or longer to process them. If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it. If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return.
To amend, click here:
https://ttlc.intuit.com/replies/3288565
