French phrase
Comment appliquer ~ ?
Meaning
How do you apply ___?
When to use it
This asks how to apply something. It is polite and seeks practical guidance on method.
Example dialogue
Comment appliquer la crème solaire ?
How do you apply sunscreen?
Il faut en mettre suffisamment et l'étaler sur tout le visage.
You need to apply enough and spread it over your whole face.