The case is here:
I decide to use Rabittmq-Server as interface for request input and using my own charm fro connect to the rabitt mq and process the the requests!.
How can I relate this two ( my charm and Rabittmq-server ) together?
If you want to write a charm, a good place to start is with the official documentation:
Specifically in your case, you will need to add a requirement to your charm's metadata.yaml file to indicate that it needs to access the RabbitMQ interface of the rabbit charm.
You will then need to create hook files to manage the connection between your charm and rabbit. I would suggest also looking at the source for the rabbit charm, which will give you a better idea of what information it is possible to transfer using this service