Installing MobArena is as easy as these four steps:
The folder structure is thus:
plugins/ MobArena.jar MobArena/ config.yml announcements.yml
At this point in time, you're probably eager to skip ahead to the arena setup page, but make sure to have a look at setting up the config-file to your liking. The config-file is where you customize the MobArena settings, classes, waves, and rewards.