You just prepare and file your 2018 return normally. You do not mention anything about what you did for 2017. If you did not prepare a 2017 return then you have nothing to transfer in to start your 2018 return, and so you will be starting it from "scratch." If you did not file a 2017 return then when it asks you for a 2017 AGI, use "zero" in order to e-file your 2018 return.
A 2018 return can be e-filed up to October 15, 2019; after that e-filing will be closed and 2018 returns will have to be printed and mailed. if you are getting a refund for 2018 there is no penalty for filing late. If you owe tax due, then your penalty and interest began to add up after April 15, 2019--so get it prepared and filed as soon as you can. TurboTax does not calculate the late penalty/interest. The IRS calculates it and bills you later.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
