Currently there is not much that is needed to be written here.
Download the setup at http://www.nymphicusapp.com/chapper/ and run it. Be aware that Chapper needs .NET 4.5 and sadly this is not available on Windows XP.
After installation and on the first start Chapper will open a windows where you have to authorize Chapper to get access to your App.net account (only a token will be stored on your harddisk – the password is neither stored nor even known to Chapper).
After authorization has completed the main window opens showing the three tabs for “My Stream”, “Mentions” and “Private Messages” showing the most recent items there. An auto refresh is done every 20 seconds.
To create a new post simply enter the post text on the textbox to the bottom and press the send button (or ctrl-enter). Use the trashcan icon if you want to start over with your post, reply or private message.
To reply to a post, send a private message, star or repost a post use the buttons on the bottom of every post.
This documentation is going to be extended during the process of creating Chapper 1.0.