Hopefully, this is what you're wanting.
Here is the page where you can purchase 2018 TurboTax software as a download to install on your computer.
https://turbotax.intuit.com/personal-taxes/past-years-products/
If that's not what you want, then please explain IN FULL. You may have to write more than 1 sentence about what you mean when you say "I need to download the Turbotax software but, I can't."
We don't know what you mean by "I can't." You'll have to describe the roadblock.
