I'm an existing user, bought this years product at Cosco. Where do I put license code?

[xmasbaby0]

You appear to be posting from online software    (online Self-Employed)   instead of the desktop CD/download software that the license code is for.  If you are using online, you are using the wrong program.  You need to switch to the desktop software to get what you paid for.  You have to download it, update it and open it up from your own hard drive to use it.  

https://ttlc.intuit.com/community/choosing-a-product/help/how-do-i-switch-from-turbotax-online-to-th...

[DoninGA]

After you install the software you purchased from Costco on your personal computer, there will be an activation screen for entering the License code after you start the TurboTax program software.