What do you mean the Online version? The Online version where you go online and log in with your username and password? Or that you just downloaded the desktop program by going online? Yes you need the 16digit License Code to activate the program after you install it.
Where to find the License Code
https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/852973
How to get started with the Desktop program, install and activate it
https://ttlc.intuit.com/turbotax-support/en-us/help-article/product-delivery/download-software-turbotax-com/L7u9oLEkq_US_en_US?uid=luqgvzrd
Did you already start in the Online version? If you started in the Online version you can switch to the Desktop program and continue without paying for Online. How to switch…….
https://ttlc.intuit.com/community/choosing-a-product/help/how-do-i-switch-from-turbotax-online-to-the-turbotax-software/00/26129