If your 1040 of 2018 is accepted then you can amend on turbo tax. As go along at one of the step you will be asked about revisit your original 1040 of 2018. revisit your income section where you will see fidelity logo click it and log to your fidelity account and transfer all tax forms. uncheck forms you have already included. Check only tax forms of fidelity those are missing. Tubo tax at end will generate 1040X, print it and mail it as per the instructions along with your payment to IRS.