How to increase the upload file size limit ?

[Paulus-dom]

When I try to upload a picture bigger than 2MB with a community user (non admin), the browser respond that the file i too big to be uploaded.
How can I increase the max file size limit ?
I tried to edit /var/www/html/piwigo/_data# cd templates_c/xxx.add_photos.tpl.php and to change :
max_file_size : '<?php echo $_smarty_tpl->tpl_vars['upload_max_filesize']->value;?>',
with
max_file_size : '4000mb',
It uploads file, but if i try to create a new album there is a bug.
Thanks for you help!