Hii EveryOne

We have two prog :
1- Client that represents the interface (Created by : QtQuick/QML) for entering data
2- Serveur Web (Java/JEE) that should menage the database

Communication between Client(Qml, Qt/C++) and Serveur Web should be done by : Webservice : Rest

I'm beginner in Webservice, I don't know where to start.
How can I establish the communication?
Steps to follow?

Cheers,