lmsPublishExample.js

import { LightningElement } from 'lwc';
import { MessageContext, publish } from 'lightning/messageService';
import ACCOUNT_SELECTED from './accountSelected.js';

export default class MyComponent extends LightningElement {
    @api recordId;

    handleAccountSelect() {
        const message = { recordId: this.recordId };
        publish(this.messageContext, ACCOUNT_SELECTED, message);
    }

    connectedCallback() {
        this.messageContext = MessageContext.getInstance();
    }
}