If you do not have any income except the income on your Form 1042-S and by code 4 is exempt under a tax treaty, you do not have a tax filing requirement for 2018.
For 2018 if you did have a filing requirement you would need to file a US resident return. As you are a US resident starting in 2018, you no longer need to file Form 8843. That form is only for nonresidents.
For year 2017, you will need to file a nonresident return and you can attach Form 8843 to the 1040NR return.
TurboTax does not support nonresident returns.
However we have a partnership with Sprintax offering a
nonresident tax filing solution to our TurboTax customers.
Visit
the TurboTax/Sprintax site for more info or to get started.
