As a international student I filed through turbo tax. This is my first time I tax filing in US. I got federal refund for education purpose which I am not supposed to get. I learnt that to amend the tax return, I have to sent these docs (1040NR, 8843 and 1040X form) to Austin. But how do I exactly return the amount to them. Do I have to enclose a check along with the documents? Or shall I ask them for a account number where I will transfer the money! And do I have to write amend at the top of the forms?

On form 1040X you will calculate the difference between the refund you got and the refund you should have gotten based on the non-resident alien return. If the difference is in the favor of the IRS you would include a check to the United States Treasury with your amended return. Be sure to write your name, address, SSN, the tax year and the form you filed (1040NR) on the check.
You do not need to write amend on the tax forms, the 1040X takes care of that.

Thank you very much for the information. But exactly whom to address in the check? "US Department of Treasury"? And the other forms 8843, 1040NR and W2 paper, do I have to send these documents also or only 1040X will do?

A I said you write a check to the "United States Treasury". You need to send form 1040X and a complete non-resident alien return, meaning all the forms

Thank you for your help!