I received an email the the TurboTax is ready to download, I press the download but nothing is happening. Didn't see anywhere to enter the installation key.

First, make sure you do not have a glitched link downloaded on your computer by checking your programs. 

If you do, uninstall it, reboot your computer and use the link provided below with the IKC already provided: 

Here is the 2018 TurboTax software download link: https://turbotax.intuit.ca/product/download/index.jsp