Have you looked at how the file plugin does this?

Thank you. I'm going to try. 

Hi.

I tried this in my input form:

<dd><?php echo elgg_view('input/file', array('internalname' => 'image', 'value' => $image)); ?></dd>

this in my /action/edit.php:

if($image)

{

$filehandler = new ElggFile();

$filehandler->owner_guid = $entity->owner_guid;

$filehandler->setFilename($prefix . $image);

$filehandler->open("write");

$filehandler->write(get_uploaded_file('upload'));

$filehandler->close();

$filehandler->save();

$gg = $filehandler->getGUID();

        }

$entity->addRelationship($gg, 'photo');

$entity->image_guid=$filehandler->guid;

And this for view the image:

     <?php 

$imagen = get_entity($vars['entity']->image_guid);

echo "<img src='{$imagen->getFilename}' border='0' width='300' height='100'>";

?>

The image appears tu save correctly and i can obtain the guid of the image. But when i get the entity for this guid the methods for ElggFile aren`t going. Anybody can see what's the problem.

Sorry, but i'm really a newbie on elgg and php. Thanks.