How can i trigger an action manually?

Use do_action, you can just:

do_action( 'my_action');

if your action has a callback function that need arguments say:

function my_callback( $an_array ){
  //use the array for something here
   var_dump($an_array);
}
add_action( 'my_action', 'my_callback' );

you can specify it in the do_action like this:

do_action( 'my_action', array( 'array_for_callback') );