Angular 5 Structural Directive

I'm trying to create a reusable search box component currently my setup is this.

search.component.html

<div class="search-box-container">
  <fa-icon class="search-icon" [icon]="faSearch"></fa-icon>
  <input type="search" name="search" class="search-box" autocomplete="off" />
</div>

search.component.ts

import { Component, OnInit } from '@angular/core';
import { faSearch } from '@fortawesome/free-solid-svg-icons'

@Component({
  selector: 'app-search',
  templateUrl: './search.component.html',
  styleUrls: ['./search.component.scss']
})
export class SearchComponent implements OnInit {
  faSearch = faSearch;
  constructor() { }

  ngOnInit() {
  }

}

and I want to use it accross multiple components like this:

<app-search [ngModel]="searchString" (onUpdate)="updateSearch"></app-search>

My question is how do I access the parent ngModel and onUpdate set in the main component inside of a structured component.