Reservations allow you to create player codes in preparations of events. This way you don't have to generate random codes right before the game starts, but instead you can generate codes up to 7 days before your event starts. You then have ample time to communicate these codes to your players so that they can join the game when it starts.
A few days before the event
It is good practice to add a few instructions in the email you are sending to your players, like how to connect to the game, how to connect to the livestream, ...
On the day of the event
You are now ready to go. Good luck, and have fun!