You just need to amend your Form 1040 to Form 1040NR.
Here are the steps:
You would need to submit both the Form 1040-X and Form 1040NR together:
https://www.irs.gov/pub/irs-pdf/f1040x.pdf
https://www.irs.gov/pub/irs-pdf/i1040x.pdf, page 7 under Residents and Nonresidents
You just need to amend your Form 1040 to Form 1040NR.
Here are the steps:
You would need to submit both the Form 1040-X and Form 1040NR together:
https://www.irs.gov/pub/irs-pdf/f1040x.pdf
https://www.irs.gov/pub/irs-pdf/i1040x.pdf, page 7 under Residents and Nonresidents