In the absence of any info, I'll assume you are asking about getting a copy of a 2018 return you've filed that you prepared in Online TurboTax. Once you log into your account, scroll down to the section "Your Tax Returns & Documents." Expand that section and choose the tax year you want. Then choose the link "Download/print the PDF."
If you don't find evidence of your 2018 return in that account, we can tell you how to look for multiple accounts.