To speed up or slow down a video in Premiere Pro:

1. Speed/Duration: Right-click the clip > “Speed/Duration” > Adjust percentage (e.g., 200% for faster, 50% for slower).

2. Rate Stretch Tool: Press R, drag the clip’s edge to adjust speed.

3. Time Remapping: Right-click FX badge > “Time Remapping > Speed” > Add keyframes and adjust the line for custom speed changes.

Use Optical Flow for smoother slow motion and keyframes for speed ramps.