There are a couple of different ways to assign guests to each event. 

From the edit/view guest option there will be a simple table of scheduled events which allows you to check boxes against each guest name individually. 

You can also choose which guests to invite to each celebration from the event manager. When you choose to 'View details' of the designated event there is an option to 'bulk assign guests'. This will allow you to assign from a list of all the guests that aren't currently invited to the event.