Filers who used the online product to file their 2018 tax return should be able to access it using this link: https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/27010
If you filed your 2018 tax return using TurboTax online, please follow the instructions in thisTurboTax Help topic.