Install CKEditor on Laravel-admin

At first, install CKEditor on laravel-admin follow the steps below.
https://github.com/laravel-admin-extensions/ckeditor

Adding file upload function on CKEditor

config/admin.php


...
        'ckeditor' => [
            'enable' => true,
            'config' => [
                'filebrowserImageUploadUrl' => '/admin/fileupload', // Add here
            ]   
        ]   
...

Another options here.

app/Admin/routes.php


use Illuminate\Routing\Router;
 
Admin::routes();
 
Route::group([
    'prefix'        => config('admin.route.prefix'),
    'namespace'     => config('admin.route.namespace'),
    'middleware'    => config('admin.route.middleware'),
    'as'            => config('admin.route.prefix') . '.',
], function (Router $router) {
 
    $router->get('/', 'HomeController@index')->name('home');
    $router->post('/fileupload', 'FileuploadController@index'); // Add here
    ... 
});

app/Http/Middleware/VerifyCsrfToken.php


<?php
 
namespace App\Http\Middleware;
 
use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as Middleware;
 
class VerifyCsrfToken extends Middleware
{
    /** 
     * The URIs that should be excluded from CSRF verification.
     *
     * @var array
     */
    protected $except = [ 
        '/admin/fileupload', // Add here
    ];  
}

app/Admin/Controllers/FileuploadController.php


<?php
 
namespace App\Admin\Controllers;
 
use App\Http\Controllers\Controller;
use Illuminate\Http\Request;
 
class FileUploadController extends Controller
{
 
    public function index(Request $request)
    {   
        $image     = $request->file('upload');
        $name      = substr(str_shuffle('1234567890abcdefghijklmnopqrstuvwxyz'), 0, 12);
        $extension = $image->getClientOriginalExtension();
        $newname   = $name . '.' . $extension;

        // you can change third variable as filesystem you want.
        $image->storeAs([ANY_DIRECTORY_YOUWANT], $newname, 'public');
        $url = [YOUR_PUBLIC_PATH] .$newname; 
 
        $param = [ 
            'uploaded' => 1,
            'fileName' => $newname,
            'url'      => $url
        ];  
 
        return response()->json($param, 200); 
    }   
}