You can achieve this using either the Narrative Design or Action features in Convai.
With Narrative Design, you can set up sections in convai.com and trigger specific events, when those sections become active. Alternatively, with the Action feature, you can configure custom behavior directly tied to the user’s input.
These kinds of custom implementations depend on your setup, but the following documentation will guide you through both approaches:
Narrative Design:
Action System:
Other users’ solution: Play videos on command - #9 by Luca_Trianti