Install ffmpeg on Mac:
sudo port install ffmpeg
Vimeo has a 500MB filesize limit in the basic account, so you might want to reduce the file size to the limit, if it is too large. Let's say you have a 20min video file, which is too large. Then you have to reduce the bitrate for encoding:
(500 MB * 8192) / (20min * 60) = ~3413 kilobits/s
Minus the bitrate for audio: