Have you already filed?  

If you have already filed, you might not be able to go back to fix.  You can return to the program to make corrections without amending only if your return is being rejected. If your return is accepted, to edit your information, you will have to amend it. You cannot just go back to edit.

If your return got rejected for any reason, you can return to the program/account to edit information along with other changes and re-submit it. For instructions, click here Fix a reject 2019.  You do not need to file an amendment 1040-X.

If your return has been accepted, you will have to amend by filing a Form 1040-X.  Click here for instructions Amend 2019.   Please note that the amendment form is not available to use until 2/12/2020.  Please come back later. 

or if you mean you typed in the wrong amount from your W-2 and need to edit that and can't navigate back there try this;

1. call up your return (if you're not already in it)
2. across the top just below the blue header you should see a tab labeled "FEDERAL TAXES", click that
3. then just below that you should see an oval bubble called "Wages & Income", click that
4. then you should see around the middle of the page blue colored bubble called "I'll choose what I work on", click that
5. then you should see in the middle of your screen "Wages and Salaries Form W-2" (the 2nd section) off
6. to the right you should see an "Update" button, click that

hopefully that's what you were looking for