My tax return completed using the free version. I assumed it would ask for my code from the Turbotax Deluxe that I purchased at Costco, it didn't. How do I enter it?

There are no license codes when using the online editions. 

That is only for the desktop CD/Download edition which you should have installed on your personal computer since you paid for the software.

If you used the Online Free Edition there is no charge.  And You can not apply the Desktop CD/Download program purchase to the Online web version. They are completely separate and different and are priced differently. You would need to get a refund for the CD and pay for online separately. And state is a separate additional charge in online.

You can move your online return to your computer for free and file from the Desktop program.  Were you able to install the Costco CD?  To continue in the desktop version see this…….
https://ttlc.intuit.com/community/choosing-a-product/help/how-do-i-switch-from-turbotax-online-to-the-turbotax-software/00/26129