A webEdition document type is a collection of properties that contains:
The document types are listed in the webEdition menu under "New → webEdition Page → …". That way it's easy for editors to quickly create a document with sane presets.
In menu "Preferences", choose "Document Types"
Create a new one, call it "Standard Page" (for example) and specify the template from the previous example ("page.tmpl").
In Defaults, also select this template (a document type may refer to several different templates) and as extension, choose ".php" and "dynamic". You can also set a default directory and language, just try it!