IngestThe keys are the part worth learning, and there is a way to practice them that cannot hurt anything. Choose Help, then Open Practice Folder. Ingest builds about thirty throwaway images and opens them, and the status bar tells you which keys to try. Nothing in that folder matters, so tag, rate, label, and undo as roughly as you like.
Press ? at any time for the shortcut sheet, or ⌘K to search every command by name. Tap and release ⌘, then press and hold it again to see contextual shortcuts. The complete list lives on the shortcuts page, and the Getting started guide walks one card from insert to finished folder.