Putting a Layer in a Timeline
example>>>
The easiest way to get started is to make a layer, select it in the document window, and then drop it in the timeline panel in the frame area.
Or
Select the layer in the document window and choose: Modify>Timeline>Add
Object to Timeline
It's a good idea to name your layers so they are easy to find on the timeline. Select the layer in the document window and name it in the properties panel.