In Laravel, how to depedency inject service into controller method

Sorry for newbie question, but I cant find any example on how to actually use Service Providers (Laravel documentation shows only how to create them).

Since Laravel's paginator doesn't work with grouping, I want to create my own paginator service, but I dont know how to inject said service into controller. Forum controller throws me exception: Class App\Http\Controllers\CustomPaginator does not exist, but I thought that if I bind service class to service container, it can be resolved using custom name?

Here are the files:

app/Http/Controllers/For

<?php

namespace App\Http\Controllers;

use App\ForumModel;
use Illuminate\Http\Request;

class Forum extends Controller
{
    public function index($page = 1, CustomPaginator $paginator)
    {
        $topics = ForumModel::orderBy("sticky", "DESC")->orderBy("lastpost", "DESC");

        return view("forum", ["topics" => $topics]);
    }
}

app/Providers/CustomPaginatorServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;

class CustomPaginatorServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap the application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        $this->app->bind("CustomPaginator", CustomPaginatorServiceProvider::class);
    }

    public function a()
    {
        echo "It works!";
    }
}

Providers table in app config

'providers' => [

    /*
     * Laravel Framework Service Providers...
     */
    Illuminate\Auth\AuthServiceProvider::class,
    Illuminate\Broadcasting\BroadcastServiceProvider::class,
    Illuminate\Bus\BusServiceProvider::class,
    Illuminate\Cache\CacheServiceProvider::class,
    Illuminate\Foundation\Providers\ConsoleSupportServiceProvider::class,
    Illuminate\Cookie\CookieServiceProvider::class,
    Illuminate\Database\DatabaseServiceProvider::class,
    Illuminate\Encryption\EncryptionServiceProvider::class,
    Illuminate\Filesystem\FilesystemServiceProvider::class,
    Illuminate\Foundation\Providers\FoundationServiceProvider::class,
    Illuminate\Hashing\HashServiceProvider::class,
    Illuminate\Mail\MailServiceProvider::class,
    Illuminate\Notifications\NotificationServiceProvider::class,
    Illuminate\Pagination\PaginationServiceProvider::class,
    Illuminate\Pipeline\PipelineServiceProvider::class,
    Illuminate\Queue\QueueServiceProvider::class,
    Illuminate\Redis\RedisServiceProvider::class,
    Illuminate\Auth\Passwords\PasswordResetServiceProvider::class,
    Illuminate\Session\SessionServiceProvider::class,
    Illuminate\Translation\TranslationServiceProvider::class,
    Illuminate\Validation\ValidationServiceProvider::class,
    Illuminate\View\ViewServiceProvider::class,

    /*
     * Package Service Providers...
     */
    Laravel\Tinker\TinkerServiceProvider::class,

    /*
     * Application Service Providers...
     */
    App\Providers\AppServiceProvider::class,
    App\Providers\AuthServiceProvider::class,
    // App\Providers\BroadcastServiceProvider::class,
    App\Providers\EventServiceProvider::class,
    App\Providers\RouteServiceProvider::class,
    App\Providers\CustomPaginatorServiceProvider::class

],