1. With no app_info.xml, attach to the project, and download at least one task. That will also get the application downloaded.
  2. Quit BOINC
  3. *Then* add the app_info.xml to the project directory. Make sure the app name in the app_info.xml matches the actual app name (downloaded in #1)
  4. Start BOINC
  5. The downloaded task will get removed, new apps will be downloaded, and crunching will begin.