How do I create a new webpage in the Documentum front end Webtop?
Why WebTop? You should use Web Publisher which is built on WebTop with the specific purpose of managing web content. Is this an OOTB installation? Web Publisher / WebTop requires significant amount of customization in order to start being useful. Do you have templates defined? If so, then just go to File New and select your template.
http://www.dmdeveloper.com/ Is a good site with some very good how-to's.
The short answer is that it can not be done.
WebTop is Documentum's generic application for browsing their back-end content repository. Think of it as a web-based Windows Explorer on steroids. It's a tool for storing, versioning, and sharing electronic documents (Word, Excel, etc.) - it's not a tool for creating web pages.
Documentum's Web Content Management product is called Web Publisher. It is the tool that companies use to allow non-technical business users to create and edit web pages.