And to start over in the Desktop program would mean to start a new return to transfer into. Go up to File-New. You will need to have the .tax2017 file on your computer to transfer from. Otherwise you will have to manually enter any prior year info, carryovers, depreciation etc.
Sorry, but there is no way you just used the Online program to file a 2016 return, since only the 2018 program is available in TurboTax Online.
The original post in this thread could actually be a few years old. A lot of these threads with that apparent early June posting date or late May posting date were moved to this new forum from the old AnswerXChange, and unfortunately and confusingly, all were given a date as of the transfer date even though many are 1,2,3 years old.
If you had read the prior posts above YOU CAN NOT TRANSFER 2017 after you have started 2018. You will have to clear and start over if you want to transfer. Or in the Desktop program you can start a new return, go to FILE - NEW. You can only transfer at the very beginning before you start.
In the online version you may be able to perform a transfer if you clear the return.
FYI ... the very first point of business when you log into the online version is the option to transfer the prior year returns from where ever you have them saved. If you missed the very first screen instructions you have to clear and start over OR just input any pertinent info as needed. Always keep a PDF and .taxfile of the filed return so you always have access to the info when required.