Yes. At the end You will need to enter 0 for the 2018 AGI since you didn't file 2018 on time.
Do you still need to file 2018? Online is only good for 2019. To do a prior year return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
You will need a full Windows or Mac to install it on.
