I go to Export -> Movie. Pick whatever format. And nothing happens. Literally.
This has been reported here: http://www.pencil2d.org/forums/topic/cant-export/, however, a resolution was not found. @Mikshaw mentions that you may have to install ffmpeg on Mac. Alas, I do not know how to install such thing (I downloaded it, but the binary is just a shell program - it doesn’t perform any sort of installation).
Other export functions such as Image Sequence work fine. I suppose I could use it to get the images and them compile them into a movie. But of course, this is not optimal.
http://ffmpeg.org/download.html
Many open source projects, particularly commandline programs, don’t always have installers. Sometimes this presents a problem, especially if they also don’t have binaries available, but sometimes it’s not as difficult as it might seem.
If you have a static binary built to run in OSX (see the link above), you should be able to just drop it into one of your bin directories (/usr/local/bin or ~/bin is recommended for programs not added by a package manager), and make sure the binary is set to be executable.
I have zero experience with OSX, but since it is Unix-based i’m making the assumption that this works. Otherwise Apple has done some weird things with the file system. If it doesn’t work this way, then try the Windows approach: Create a “plugins” directory in the Pencil2D directory and drop the ffmpeg binary into that. I can’t guarantee either one, but i can’t see why it wouldn’t work one way or the other.