(Optional) Create a new world so you can challenge yourself from scratch.
Install the data pack by dropping the .zip file into your world's datapacks folder.
Set the timer using the command: /function onehourtodragon:onehourtodragon
Get moving! Start scrambling to collect diamonds (or beds).
After you start the command you and everyone else on the server—whether you are playing solo or scrambling with a full 25-player lobby—will be automatically teleported to the End to face the dragon.
Too easy for you? See if you can pull it off in even less time by using the command /function onehourtodragon:timetodragon {time:<int>} (replace with an integer in minutes).