Below are 2 basic steps to create simple event in LWC:
Step 1 : Create Event using new Custom Event Method
const events = new CustomEvent("YourEventName");
Step 2 : Dispatch Event using Dispatch Event Method
this.dispatchEvent(events);
for example:
childcmp.js
import { LightningElement} from 'lwc';
export default class ChildCmp extends LightningElement {
handleEvent(){
// create event
const events = new CustomEvent("sampleEvent");
// dispatch event
this.dispatchEvent(events);
}
}