How to insert an intro, game or other external stuff in an existing Captivate project?

I am using Captivate 9. I can therefore use the assets library of e-learning brothers.com. But nowhere I can find an explication how to insert an intro, that I downloaded and changed for my project, in my existing project. As I see now, I have two Captivate projects, but I don't see a possibility to integrate them in one.