What format do apps have to be in for OS X Profile Management?

Title says it all: under servername.local/profilemanager/, in Device Groups, Users, or Groups, in what format can I upload apps? Clicking on the settings icon on the bottom of the page, and then choosing Edit Apps, a pane pops up which allows me to upload apps. I don't know what format, though, and everything I try (either pkg, mpkg, app, ...) get rejected with a Filetype Not Supoorted error. What do I need to do?