See this TurboTax support FAQ for upgrading to Plus - https://ttlc.intuit.com/questions/2586262-how-do-i-purchase-turbotax-plus-so-i-can-get-my-tax-file
If you did not use TurboTax for 2017 see this TurboTax support FAQ - https://ttlc.intuit.com/questions/3355526-what-if-i-need-a-prior-year-turbotax-online-return-and-i-m...
