Make sure the headlights are completely dry and that it isn't going to rain/snow in the near future, or that you have a well-ventilated, covered space to work in.

Shake the clear coat well and apply a thin coat evenly across the entire headlight, using long, quick strokes to avoid pooling.

Wait for the clear coat to fully dry before applying the next coat. Apply at least two coats for better results.

Read the product label and follow the manufacturer's application directions

Do not apply clear coat in poorly ventilated conditions.