class 'Form' not found

1. composer.json 

require 부분에

"require": {
    "php": ">=5.5.9",
    "laravel/framework": "5.2.*",
    "laravelcollective/html": "~5.0"
},

요렇게 추가한다.

$ compser update 잊지 말고 실행

2. config/app.php에 아래로 내려보면..

'providers' => [

위에 생략...
Illuminate\Session\SessionServiceProvider::class,
Illuminate\Translation\TranslationServiceProvider::class,
Illuminate\Validation\ValidationServiceProvider::class,
Illuminate\View\ViewServiceProvider::class,
Collective\Html\HtmlServiceProvider::class,

하나 더

'aliases' => [

위에 생략

'Storage' => Illuminate\Support\Facades\Storage::class,
'URL' => Illuminate\Support\Facades\URL::class,
'Validator' => Illuminate\Support\Facades\Validator::class,
'View' => Illuminate\Support\Facades\View::class,
'Form' => Collective\Html\FormFacade::class,
'Html' => Collective\Html\HtmlFacade::class,

이렇게 추가

Form이 잘 될거시다!!