Use the sidebar (or the Filters button on mobile) to filter by a person or event — this shows only the photos relevant to you.

Click "Select & Download" in the top bar to enter selection mode.

Tap individual photos to select them (on desktop, Shift+click selects a range). A red checkmark appears on each selected photo.

Hit "↓ Download selected" to save your chosen photos, or "↓ Download all visible" to grab everything currently shown.