I don't want to download turbo tax, can I add a license code to the online version

[DoninGA]

There is no license needed to use the TurboTax online editions.

If you do not want to use the TurboTax desktop download editions, then you need to ask for a refund from where you purchased the desktop edition license code.

[RachelW33]

No, you cannot use a license code for the online version.  If you purchased the download version of Desktop, you can contact customer support to see if you can get a credit for TurboTax Online.  Please see How do I contact TurboTax?