First of all, you are not supposed to use TurboTax to file your taxes because you are a nonresident for the current tax year.
As an F-1 visa holder, you are considered as "exempt" meaning not counting days for five years starting from the date of your first arrival in the United States. After the five years period, you will start counting days by using the Substantial Presence Test to see if you qualify to be treated as a US resident for tax purposes.
In your situation, you are considered as a nonresident from 2014-2018 filing a Form 1040NR. Starting from 01/01/2019, you will start counting your days. If you meet the Substantial Presence Test in 2019, you will be considered a US resident for tax purposes and file a Form 1040 for your tax year of 2019.
As TurboTax does not support Form 1040NR, you are advised to use Sprintax, our partner who offers filing solutions to our customers. See Visit the TurboTax/Sprintax site
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