open Turbotax business there you should see a link for an extension.
for a calendar year S_corp the extension is due 4/17 by midnight local time. after that I don' think Turbotax will allow yo to e-file an extension because its invalid. If you can't file a timely extension, then get your S-Corp done as quickly as possible the penalty for late filing is about $200/month/shareholder for up to 12 months
if you are penalized, you can try filing for penalty abatement on IRS form 843.
You may qualify for the “one-time” abatement of the late file penalty for the first late-filed tax year. You may also be able to argue that you had “reasonable cause” to be late with filing if the business was brand new and you weren’t yet up-to-speed with all the requirements to be in full compliance.