To animate a blend shapes 3D model, adjust each blend shape’s weight values over time in 3D software—this transitions the base mesh between target shapes (like neutral to smile).
Blend shapes merge a base model with pre-made targets, so animation means setting how much each target influences the base at different frames (e.g., "smile" weight from 0 to 100% over 2 seconds for a grin). Tools like Blender, Maya, or Unity use timeline keyframes to link weights to smooth animation curves.
For beginners, try Blender: add simple blend shapes (blink, frown), then set weight keyframes in the Dope Sheet. This builds timing skills without complex rigs.