If the IRS rejects your return, sign in to your account and you should be taken directly to a screen titled FreeTaxUSA Rejection Notice. (If you're not taken directly to this screen, you can access it from the Filing menu > Check Status.) On this screen you'll find additional information that applies to the rejection. Click the Continue button to access your return and correct any errors or information that needs correcting.
To get to the screen where you need to fix the error, use the menu (Personal, Income, Deductions, Misc, Summary, etc). Once you navigate to the screen and fix the error(s), then you can send your return again from the Filing menu.
If you need to change your prior year AGI or PIN info, you can go back to that screen by choosing Filing in the top menu, then Electronic Signature (Self-Select PIN).
When you are ready to send your return again, select the Filing menu option and follow the screens until you get to the Submit Return for Processing screen. Click Send Tax Return to resubmit your return.