In French, "You're welcome" is "de rien." It translates literally as "of nothing," but is used to mean "you're welcome" in a "think nothing of it" kind of way.
Alternatively, you could just smile and nod - you don't need to verbally respond to a thank-you, but it is polite to!
You could also say "Je vous en prie," but this is much more formal and you wouldn't really use it when talking to your friends.
If you were staying in a hotel, the manager might say it to you if you thanked them for their help. You probably won't need to use this very often in speech, but it's useful to know what it means in case somebody says it to you!
Using "You're Welcome" In Conversation
"Merci!" / "De rien!" = "Thank you!" / "You're welcome!"
