<entity>Controller.php

<?php
use Modules\Media\Http\Controllers\Api\MediaController;

    /**
     * Store a newly created resource in storage.
     *
     * @param  Request $request
     * @param  Route $route
     * @param  MediaController $media
     * @return Response
     */
    public function store(StoreGameRequest $request, MediaController $media)
    {
        $this->game = $this->game->create($request->all());

        if($this->game->id) {
            // Get mediaId and zone from request
            $mediaId   = $request->get('mediaId');
            $mediaZone = $request->get('mediaZone');

            if($mediaId && $mediaZone) {
                // Link media file with entity
                $mediaData = [
                    'mediaId' => $mediaId,
                    '_token' => csrf_token(),
                    'entityClass' => (new \ReflectionClass($this->game))->getName(), // You can also hardcode entity here if you like
                    'entityId' => $this->game->id,
                    'zone' => $mediaZone
                ];
                $req = Request::createFromBase(Request::create('', 'POST', $mediaData));
                $res = $media->linkMedia($req);
            }

            flash()->success(trans('core::core.messages.resource created', ['name' => trans('<module_name>::games.title.games')]));
        }
        return redirect()->route('admin.<module_name>.<entity_name>.index');
    }