How do I file for my 2008 taxes?

2008 - 12 years ago?   Or is that a typo an you mean 2018?

TurboTax online and e-file for 2018 ended on Oct 15, 2019. 2018 (and earlier tax years) can now only be completed using the CD/download software installed on a Mac or Windows computer. The return must be printed, signed and mailed.

2016-2018 software can be purchased here:
https://turbotax.intuit.com/personal-taxes/past-years-products/

2008?  Why do you need to file a 2008 tax return from 11 tax years ago?

Or did you mean 2018?

To complete and file a 2018 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2018 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/

A 2018 tax return can only be printed and mailed, it cannot be e-filed.