Hi Cedric,
First of, I have a couple links of recommended reading for you to get started with:
https://nodered.org/docs/user-guide/messages
https://nodered.org/docs/user-guide/nodes
After reading those, do you have an idea to continue?
For future messages, it often helps if you include the (relevant part of the) flow you've made to a post. You can get it by going to the hamburger menu in Node-RED (3 horizontal lines) -> export -> copy the flow (double check if you're only copying the currently selected node or the part that you were actually trying to send), then add it to a post following the following instructions: How to share code or flow json
That way users helping you can import the exact code and look at it.
