Once you have a Raspberry Pi setup properly with your connectivity mode of choice (for example, wifi), you can install the script using this:
curl https://raw.githubusercontent.com/GovLab/berrycast/gh-pages/install.sh | sudo sh
You can preview the content that will be displayed at:
https://govlab.github.io/berrycast/<IP>
So, for example, https://govlab.github.io/berrycast/192.168.0.11.