If you have already e-filed or mailed the return and they accept it, then you will need to wait until you have received your refund. Then, you will need to amend that return to make changes (add your 1099-R). You will need to send in any forms that caused the need for an amendment (Original 1040 Form, new 1040X Form and 1099-R. Print, sign and mail your forms to the IRS.
If you have already e-filed or mailed the return and they accept it, then you will need to wait until you have received your refund. Then, you will need to amend that return to make changes (add your 1099-R). You will need to send in any forms that caused the need for an amendment (Original 1040 Form, new 1040X Form and 1099-R. Print, sign and mail your forms to the IRS.
I should have said I was a dependent but I claimed myself
Did you say you could not be claimed as someone else’s dependent, but it turns out your parent(s) can claim you? Now your parents’ return is being rejected when they e-file, or it will be rejected. That means your parents must print, sign, and mail their return. They can still claim you as a dependent, but they cannot e-file now.
Your part in fixing this is to wait until your return has been fully processed and you have received you refund. THEN you need to file an amended return, called a 1040X, to change the way you answered that question in Personal Info about whether you can be claimed as someone else’s dependent. You will have to print and mail the 1040X—it cannot be e-filed. You might need to repay some of your refund.