My_Test_Repo/force-app/main/default/lwc/publisher/publisher.js

import { LightningElement } from 'lwc';
import pubSub from 'c/pubSub';
export default class Publisher extends LightningElement {

    handleOnClick(){
        console.log("Event Firing");
        let message ={
            "message" : 'Hello Bro'
        }
        pubSub.fire('simplevt',message);
        console.log('Event Fired');
    }
}