The Assets Window is where you can manage your Compositions and add external assets.
To import an asset either:
File > Import Asset...
Double click in the Assets Window.
Drag external assets from your filesystem into the window.
Dragging images from your filesystem into the Viewport will also add those assets to the Assets Window.
.exr (single channel only for now)
.apng (animated pngs will often have a
.png file extension. Change this to
.apng for Cavalry to recognise it as an image sequence)
Google Sheets - see Google Sheets Asset.
The following codecs are supported for video formats:
h263, h264, h265 (hvec)
ProRes (422, 422 HQ, 422 LT, 422 Proxy, 4444, 4444 XQ)