If you incorrectly filed Form 1040 and you should have filed Form 1040-NR instead, you will have to file an amended return, Form 1040-X, and attach your Form 1040-NR tax return. You cannot do this with TurboTax. Follow the instructions under "Resident and nonresident aliens" on page 2 of the IRS Instructions for Form 1040-X.
TurboTax does not support Form 1040-NR. TurboTax has a partnership with Sprintax to prepare a Form 1040-NR federal tax return and corresponding state tax return for certain categories of nonresident aliens - international students, scholars, and non-resident foreign professionals. Click this link for the details of who can use Sprintax, and to get started.
