The Gemma theme includes 2 page templates and one post template. The included templates are:
- Full Width Post (no sidebar)
- Full Width Page (no sidebar)
- Landing Page (blank page with no header, footer, or widget areas)
To use a page or post template, edit (or create) a post/page and in the editor find the Page Attributes tab in the right sidebar.
Choose your template of choice from the Template dropdown menu.

Remember to update or save your changes.