You don't, and you can't on an iPad. The online version of TurboTax 2016 is shut down permanently and forever, so they can get the online system ready for the 2017 tax filing season.
The windows version of TurboTax Home & Business for 2016 will install and will work on Windows 8.1 or 10, just fine. Get it at https://turbotax.intuit.com/personal-taxes/past-years-products/ Make SURE you are under the correct tab for the 2016 tax year. If you purchase the software for the wrong tax year, then bottom line is, you own it.