The license code is only used on the 2019 TurboTax desktop CD/Download software that you purchased. After you install the TurboTax software on your personal computer you will be asked for the license code.
The TurboTax online editions do not require a license code and there is no reason to use the online editions since you purchased the TurboTax software to be installed on your computer. The TurboTax desktop and online editions are totally separate program with different price points.
See this TurboTax support FAQ for a license code - https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/852973
