First, slap yourself.
Second, you only file one tax return for the whole year that lists all your income. Since you filed a return already, that means you must file an amended return that adds the new income to your existing income. You will probably owe tax back to the IRS.
Wait until your original tax return is accepted, processed by the IRS, and your refund is paid. Then follow the instructions at the bottom to file an amended return. In most cases you should expect that you will owe money back. Don't file the amended return until your refund is paid. (If you are due an additional refund on the amended return, expect it to take 4-5 months to be paid.)
If you are lucky, your first return will be rejected. In that case, it is as if is was never filed, and you can add the additional income and transmit it again without having to make an amended return.
https://ttlc.intuit.com/replies/3288565
