If you have already purchased the TurboTax desktop software for 2018, sign onto your download account using the same User ID you used to purchase the software - https://shopping.turbotax.intuit.com/unified/downloads?route=myaccounts
TurboTax software purchased from TurboTax can be downloaded at any time for any reason as often as needed for up to three years from the purchase date.
If you have not purchased the 2018 desktop CD/Download editions, then go to this TurboTax website - https://turbotax.intuit.com/personal-taxes/cd-download/
I need to download turbotax deluxe 2018 for my new computer... I purchased the software at Costco in Florida and I left my CD in Florida and I'm in Ohio
You'll need to speak to Customer Support and see if they will place a download in your account. TurboTax phone support is open today until 5PM Pacific (8PM Eastern). Then opens again tomorrow 5AM Pacific (8AM Eastern).
You can use the form at the link below to schedule a call back, or it may provide a number.
Where the form asks what product you are using, be sure in the dropdown menu to indicate "CD/download" and the proper operating system, then indicate which Edition.