Click the Animate button in the mode switcher at the top of the interface, or press Ctrl+2.
The interface rearranges when Animate Mode is entered:
Record Mode is what makes property changes create keyframes automatically.
Toggle Record Mode:
Ctrl+Alt+RDefault behavior: Record Mode is automatically activated when Animate Mode is opened (configurable in Application Settings).
The playhead is the thin vertical line running the full height of the timeline. It represents the current time position.
Left Arrow / Right Arrow for frame-by-frame stepping. Home / End for start/end of the sequence.