For the S corp return you need to use the separate Business program. Turbo Tax Business is not available to do online or on a Mac. And you can have both TT Business and TT Home & Business (or any personal version) installed on your computer at the same time.
Buy the prior year Business downloads here
https://turbotax.intuit.com/personal-taxes/past-years-products/
Yes you should do the S corp return first. You will get info from it to enter into your personal return. 2018 is now the prior year. You need to use separate programs for Business and personal.
You can only buy the download for prior years. You have to buy a separate program for each year. They only sell the last 3 years. You need a full Windows or Mac computer to install it on. Buy the download here
https://turbotax.intuit.com/personal-taxes/past-years-products/
You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.
If you are getting a refund, there is not a penalty for filing past the deadline. You have 3 years to file for a refund. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.
How to file a prior year
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25...
Did you start an online return last Year? How to finish a prior year online return
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...
