As you have elected to be taxed as a S-Corp, you have to file a tax return (form 1120S) even if the S-corp did not have any income or expense in 2018.
Please read this IRS document for more information:
https://www.irs.gov/faqs/small-business-self-employed-other-business/entities/entities-4
To file form 1120S, you need to use TurboTax Business.