Unfortunately, if the tax return has already begun process, you will need to file an amended tax return.
You will need to wait until the initial tax return has been processed to file.
You can prepare the amended tax return by clicking "amend a return" after you have logged into your account.
For more information, follow these links:
What to Include with Amended Tax Returns
How to Amend
Tips to Amend
IRS on 1040X
