Hi Gilles,
You are French, so do I
Your English seems good (to me).
On the site, you can have a look on the video tutorials (mines and Ben's ones), they are all in French.
You will find there all on use of Modbus TCP/IP communication.
Just replace Modbus TCP/IP objects by Modbus RTU ones in Node hierarchy and relink them to Plant hierarchy data to make it work.
If you are a newbie, you have to know that learning Proview is a long curve, don't give up, it's really a good software, a gift for automaticians.
Have a good day
Bye
/Bruno