use Catalyst qw/
    ...
    Catalyst::Role::Messages
/;

# later...

package MyApp::Controller::Blargh;
...

sub fnargh : Local {
    my ($self, $c) = @_;
    ## do some form submission stuff
    if( $form_stuff_is_successful ) {
        $c->msg("Successful submission is successful!");
    }
}

Open up your wrapper and add these lines:
[% FOR message IN messages -%]
    [% message %]
[% END -%]

(Add formatting as you please)