My page can't find my Model. Why?

I'm new to Laravel and I'm trying to figure this out.

I'm working through the tutorial at https://www.youtube.com/watch?v=v6SZerzfgIg.

My code right now looks like this:

Here's my "home.blade.php:"

<form action="/insert" method="Post">

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My web.php page has my routes structured like this:

Route::get('/home', 'HomeController@index')->name('home');

Route::get('/display','InsertController@index');

Route::post('/insert', 'InsertController@add');

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My InsertController looks like this:

use Illuminate\Http\Request;

class InsertController extends Controller
{
	
	public function display() {
		
	}
	
    public function add(Request $request) {
		
		add::display(Request::all());

	}
   
}

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I'm thinking that "add::display(Request::all())" is targeting my "add" model sitting in my "app" directory. At that point, I've got this:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class add extends Model
{
    protected $fillable = ['question_text', 'keywords', 'required', 'type', 'answer_a', 'answer_b', 'answer_c', 'answer_d', 'answer_e'];
}

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I'm wrong, apparently. Because when I submit my form, I get this error:

Class 'App\Http\Controllers\add' not found

What am I doing wrong? And am I right in assuming that this code:

add::display(Request::all());

...is going to submit my data and then grab the "display" method and show that page?

I'm a mess...

Straighten me out, please...