For those of you who do not want to watch an entire 7:54 minutes video here is a short description of the video.
So what you need to do is to scroll down to the bottom of your config.yml
By default on the bottom you will have a couple of lines that will look like this.
Now under that you are going to add your own permissions for the arenas that you want. The permissions that you can use can be found here: http://dev.bukkit.org/bukkit-mods/myhungergames/pages/help/tutorial/getting-started/configure-the-config/
All of the permissions you add here will overwrite the ones that are above these which are global permissions. If there is a global permission that you have not added in you specific setup then it will take the value of that permission from the default config. For example
There is a permission called min-players. If you have not decalred the amount of min players in your specific setup then it will read the min players from the default config.
Now here is an example of how a small setup can look.
Now the way you add this to an arena is by adding
setup: <name of your setup>
to your games.yml like this
That is pretty much it!