If you have tax forms that needed to be reported on your tax return, and you forgot to report those forms, you will need to file and amended return and add those documents.
Please wait until the original return you file has processed. It is always possible that the IRS will catch your error and correct the return for you. (If that happens, they will send you a letter asking if you agree to their computations)
Please click here for how to amend a return you already filed