First, you need to register the variables you will be using in the template and then you need to render it.
Example from one of mine using a template_hook:
PHP Code:
$templater = vB_Template::create('my_custom_template');
$templater->register('a_variable ', $a_variable);
$template_hook['some_hook'] .= $templater->render();
or - using a variable (which must then be registered for us in the next template):
PHP Code:
$templater = vB_Template::create('my_custom_template');
$templater->register('a_variable ', $a_variable);
$somevariable .= $templater->render();
or - print_output:
PHP Code:
$templater = vB_Template::create('my_custom_template');
$templater->register('a_variable ', $a_variable);
print_output($templater->render());
There is a blog entry by Kier over on vb.com that shows this.