Perform User Authentication if condition is true

I have 2 strings

$password_api = VSE::user('password',$username); //abc
$password     = Input::get('password'); //abc

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If they're matched, I want to log the user in

if ( $password == $password_api ) {

    // Not sure what to do in here ... 
    $auth = Auth::attempt();
}

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This approach is just for the demo purpose.

How can I do that in Laravel 5 ?

Any hints / suggestion will be much appreciated

via Chebli Mohamed