Since you have already filed, you will need to wait until the IRS either accepts or rejects the return to make changes or add any additional tax forms/information. If they reject it, you just make the needed changes and re-submit the return.
If they accept it, you will need to wait until you have received your refund and then amend that return to make changes. Amended returns have to be printed and mailed in and take up to 16 weeks to be processed.
After you have received your refund, you can go here and get instructions https://ttlc.intuit.com/questions/3061514 for amending that return.
See some reasons you'd need to amend your return here https://ttlc.intuit.com/questions/1908543
