To be able to use a layout for actual page rendering, you need to declare it in layouts.xml.
Conventionally layout declaration file can be located in one of the following locations:
- Module layout declarations: <module_dir>/view/frontend/layouts.xml
- Theme layout declaration: <theme_dir>/_/layouts.xml
http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/layouts/layout-types.html