1. Go to Website > Pages and click + Add New (/admin/pages/0).
2. Enter a Title. The URL Slug is filled in automatically from the title (lower-case, words joined with dashes) – you can change it. Use Preview next to the slug to open the public address.
3. Under Template, pick how the page is built. Templates that exist for pages are listed by name; DIY (pre-selected) lets you build the page freely from modules.
4. Click Save. You are taken to the page editor for the new page, where you add modules or switch to the New Builder.

Validation: the title cannot be empty ("Title empty"), a template must be selected ("Template empty") and the slug must be unique among pages ("Url Exists in other post: …").