Can't bind to 'icon' since it isn't a known property of 'fa-icon'

Edit You can also import the ShareButtonModule which already exports the FontAwesomeModule.

Original answer

Assuming you've already installed the font awesome npm package, you need to add FontAwesomeModule to your module's imports

import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';

@NgModule({
 //...
imports: [
     //...
   FontAwesomeModule
  ],
})
export class AppModule { }  

See example here

https://www.npmjs.com/package/@fortawesome/angular-fontawesome