I'm ready to complete my 2019 return. I opened Turbo Tax and it is asking for a activation code. Where do I find it?

Here are some links depending on where you bought it.

If you Downloaded from a retailer and can't find the License Code
https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/855903

If you have the Turbo Tax CD and can't find the License Code
https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/855902

Find the License Code if you downloaded from Turbo Tax or the Advantage plan
https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/855904

See this Help article on how to find your License code. 

I have Turbotax installed and in use but when I try to open it, I am asked for my license code. I know that it is with the box that the CD came in, but I cannot find it. How can I open and access my 2019 return in progress?

I think you can ask for another License Code.

Contact Customer Service

 (You need to pick the CD/Download program in the product drop down box.) 
5am-5pm Pacific Time Monday -Friday
https://support.turbotax.intuit.com/contact/

What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632