to install an app in webedition you will have to:
1. ssh-wget download / or ftp upload the app to the webEdition/apps folder.
(do not unpack it / the apps / the *.tgz)
you can download the available (currently only 2) apps from here: http://download.webedition.org/applications/backend/third-party/
2. install it via the Extras -> Anwendungsveraltung / App Management
the buttons symbolize available apps. to install them click on them.
You need to relogin then you find the apps in the „Extras“ Menu.
More on this topic: http://www.webedition.org/de/webedition-cms/apps/