If you have not stayed in the US for more than five years by 2018, you are a nonresident. You cannot file with TurboTax, please visit our partner Sprintax to complete your filing.
If you have stayed in the US for more than five years, you are considered as a resident. As TurboTax does not support this form, you have to download the form from the IRS. See https://www.irs.gov/pub/irs-pdf/f8843.pdf
