Since pennyblack is heavily based on the feincms base model, you have to register at least one template to use it. There is a example template called base_newsletter.html in the templates folder which you could register like shown in the example project.
from pennyblack.models import Newsletter
Newsletter.register_templates({
'key': 'base',
'title': 'Generic Newsletter',
'path': 'base_newsletter.html',
'regions': (
('main', 'Main Region'),
),
})