Add a label to the Docker container

Greetings,

I’m currently using Watchtower to monitor and update my Docker containers in Portainer. However, I want to exclude the Discourse container from being updated by Watchtower.
I am not IT pro so I want to ask you for a short tutorial on what exactly I must change in my Watchtower Monitor docker-compose.yml file and other changes in the Discourse configuration.
I am glad for any help.