for example:
In your example_plugin.php file
$this->add_filter('feed_content', 'example_feed_content');
function example_feed_content($data)
{
$contents = array(
array(
'title' => 'this is the first title',
'url' => 'http://this.site.com/first-title',
'date' => 12543540, //a UNIX format date
'body' => 'This should be the body of the first item'
),
array(
'title' => 'title of the second item',
...
),
);
$this->plugin->add_filter()
)
return array_merge($data, $contents);
}