If you would like to de-activate a page and hide it from your visitors, but not delete the page this is simple to do. On the right side of the publish page there are two switches - one to disable both English and French versions (disable globally) or you can disable an entry for a specific language.
Entries in the Singles area cannot be deleted - they can only be disabled.
On the entry listing page, check the entry you wish to delete then click the gear icon at the top of the page and select Delete.