Unzip the file and drop the folder inside into your Minecraft saves folder, it should then show up in your single player worlds, or put it on a server. The recource pack is also contained within the ZIP and needs to be sent to every player.

You can play Be The Warden with your friends by starting a 2 hour free trial on the StickyPiston website. The server will stay up for a maximum of 2 hours, but you can immediately start another one!