Use the Foreground and Background layers to create a multi-layered animation. This will allow you to edit the foreground of your animation without fear of changing the background and vice-versa.
To select a layer, click on the foreground strip or the background strip until they are highlighted in blue.

To hide or show a layer, click on the little tick box underneath Foreground/Background. Turning layers on and off will help with editing your animations.
You can navigate your timeline by clicking on the blue arrow buttons on either side of your frames.

Rearrange your frames by dragging and dropping them along the timeline with the left mouse button.

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Before you start on the beautiful details of your animation, try drawing a simple outline. This way, you can get the overall composition looking great, and you can make sure everything's going to fit in the frame! Once you're filling in the details, you can start deleting your outline if you don't need it any more.