DRI provides a decent starter guide:
[list=1]In the Drobo Dashboard, enable DroboApps. I don’t have it in front of me right now, but it’s not too hard to locate.
Mount the DroboApps share, whether via Dashboard, Windows Explorer, or Mac OS X Finder, it makes no difference.
Download the app in question - it will be a “.tgz” file. Do not expand this archive.
Copy the app.tgz to the DroboApps share. Don’t put it in a folder, just at the root of the share.
[*]Restart the Drobo using the Drobo Dashboard.[/list]
Configuring each app is wholly dependent on the app and how it’s packaged and designed. If you’re going to use apps, a lot of them ultimately like to have a web server (Apache or lighttpd) and Droboadmin installed, and some will require SSH (Dropbear or OpenSSH).
Before you get too deep, keep in mind that the DroboFS has a very weak processor and very limited memory, so it may struggle with some tasks.