General developer forum

Take a look here at how to set up a filemanager element then store the files back into a location of your choice once the form has been submitted:

http://docs.moodle.org/dev/Using_the_File_API_in_Moodle_forms#filemanager

Once you have saved the files from the filemanager into your desired location, you can then access them via:

$context = context_module::instance($cmid);
$component = 'mod_certificate';
$filearea = 'whatever you called the filearea when you saved the filemanager files';
$itemid = 'whatever itemid you used when saving the files'; // Note this is not the 'draftfileid' that was used temporarilly whilst showing the filemanager on the form, but the itemid you used when saving the form data
$filepath = '/'; // Unless the file was stored in a subdirectory
$filename = 'name of the file.ext'; // The name of the file you are trying to retrieve

$file = $fs->get_file($context->id, $component, $filearea, $itemid, $filepath, $filename);

OR (if you don't know the exact name of the file uploaded by the user)

$files = $fs->get_area_files($contextid, $component, $filearea, $itemid);
foreach ($files as $file) {
...