There are two basic methods to choose from when creating animation layers. You can create a layer, or you can duplicate a layer that already contains animation. 
To create a layer:
Do one of the following: 
- Click the New Layer button in the Animation Layer editor. 
- Right-click in the Animation Layer editor and select New Layer from the context menu. 
- In the Key Controls window, select New Layer from the Layer menu. 
Note: New layers are set to Additive mode by default. 
To duplicate a layer:
- Select the layer you want to copy. 
- Do one of the following: - Select the layer you want to copy, then click the Duplicate Layer button. 
- Right-click on the layer and use the Copy and Paste options in the context menu. 
- Select the layer, then press Ctrl-C followed by Ctrl-V to copy and paste it. You can also select Edit > Copy, then Edit > Paste from the main menu.