When you are ordering the desktop editions a pop-up window asks for the Operating System you will be using, Macintosh or Windows. On the same window is a link in blue I'd like to order a CD. If you do Not click on that link then you are ordering a Download. Once purchased the download is available immediately.
TurboTax website for the desktop CD/Download editions - https://turbotax.intuit.com/personal-taxes/cd-download/