Drag the preview to aim, or use the sliders. The amber track is the Sun's path across the eclipse for your location; the Sun is drawn at even intervals as it eclipses, waxing into the corona at totality. If the path spills outside the frame, a single-frame "string of pearls" won't fit at this focal length.

▲ The hills and buildings along the bottom are a stylized reminder, not your real horizon. Click Load real horizon to replace them with actual terrain and buildings around your spot.