ProcessWire module adding Latte templates (http://latte.nette.org/) to the TemplateEngineFactory.
Install the module just like any other ProcessWire module. Check out the following guide: http://modules.processwire.com/install-uninstall/
This module requires TemplateEngineFactory: https://github.com/wanze/TemplateEngineFactory
After installing, don't forget to enable Latte as engine in the TemplateEngineFactory module's settings.