The TurboTax online editions are only for tax year 2020
If your only income from working as an employee was only $800 there is no reason to file a 2018 tax return unless you had taxes withheld and want a tax refund. Or you had state Marketplace Insurance and received a Form 1095-A then you need to file.
Or if your income was from self-employment then you are required to file a tax return.
To complete and file a 2018 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2018 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2018 tax return can only be printed and mailed, it cannot be e-filed.
