Start a new entry in a section, or a new category in a category group: open the index, choose the source and press its "New" button. The edit form opens on a new, unsaved element.
Examples
When I start a new entry in the "Blog" section
When I start a new entry in the "Pages" section
When I start a new category in the "Topics" group
When we start a new entry in the "Notes" section
And I start a new category in the "Topics" group
Pattern
When(/^(I |we )*start a new (entry|category) in the "([^"]*)" (?:section|group)$/, …)
Part of @webship-js/craft-cms-steps (github.com/webship/craft-cms-steps), a step pack for Webship-js 2.0.x.