I am an international student and I should do my tax return as a nonresident. However, I have used turbotax to e-file my forms as resident by mistake. What should I do?

You will need to file an amended return (1040X) and send it with the correct NR return.  (Unfortunately Turbo Tax does not do the NR tax but see below, there is a partner that can do it)  The form and instructions can be found at the IRS website (https://www.irs.gov/uac/about-form-1040x).  The 1040X instructions say:Resident and nonresident aliens.                             Use Form 1040X to amend Form 1040NR or Form 1040NR-EZ. Also, use Form 1040X if you should have filed Form 1040, 1040A,                     or 1040EZ instead of Form 1040NR or 1040NR-EZ, or vice versa.                                                   To amend Form 1040NR or 1040NR-EZ, or to file the correct return, do the following:                      
Enter your name, current address, and social security number (SSN) or individual taxpayer identification number (ITIN) on the front of Form 1040X.
Don’t enter any other information on page 1. Also, don’t complete Parts I or II on page 2 of Form 1040X.
Enter in Part III the reason why you are filing Form 1040X.
Complete a new or corrected return (Form 1040, Form 1040NR, etc.).
Across the top of the new or corrected return, write “Amended.”
Attach the new or corrected return to the back of Form 1040X.

https://ttlc.intuit.com/replies/4028799

How about the state tax return? I also used turbotax to do the state tax return.

Which state?

CA and NJ

CA and NJ do not have a separate for Nonresident Aliens so you will not have to amend the states, unless there are any changes on the federal that would affect the state return- check your 1040NR to see if any adjustments had to be made.

It seems I need to resend my Federal, CA, and NJ tax return form by myself.