How to get layers from the container?

Hello everybody! I am new to Adobe AnimateHello everybody! I am new to Adobe Animate. My friend sent me a ready-made banner and asked me to remake it in different sizes. But when I open the timeline I only have one layer. How can I open other layers?. My friend sent me a ready-made banner and asked me to remake it in different sizes. But when I open the timeline I only have one layer. How can I open other layers?