The idea is that if you want to describe a new feature using a mockup, create a branch of the mockups project, modify the screen of interest, save it as a png, then link to the raw png blob in gitorious from the wiki.
There was a discussion about a popup or new screen which is opened when you click on an old version of an app. In this case, to start mocking it up, you could:
- Clone "git://gitorious.org/fdroidclient-mockups/fdroidclient-mockups.git"
- Create a branch "app-version-screen"
- Edit app-details/app-details.ep in Pencil
- Save it, export png to app-details/app-details.png
- Link to the raw png blob on wiki/irc/wherever
If you are pondering a change to an existing screen, you could just modify that file. But if you are creating a whole new view, then you may prefer to just copy an existing directory, rename it, and start from there.