To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on 2018
The status of the federal tax return will be shown. If the status is Accepted then the federal tax return was e-filed and received by the IRS.
For 2018? When did you file? You had to file 2018 before last October 2019. If you think you did it online this year you have a problem. Online is only for 2019 and you can not efile 2018 anymore.