[Plugin: Lazyest Gallery] How can I add to a registered user to upload privilieges

For security reasons, users should have at least Contributor capabilities to upload images.
You can however override this by adding the following code to your (child)theme functions.php

function my_lazyest_editor( $capability ) {
  return 'read';
}
add_filter( 'lazyest_editor_capability', 'my_lazyest_editor' );