Start by clicking the edit details button to the right of the booking details on the details tab
You can opt to change the requirement for a single instance in a a series or for the current instance plus all other future instances.
Click Single or All
Click Add to add new services for one or multiple instances
Select the new service you wish to add and click Add
Confirm the new service choices and click Confirm
The new service request will be notofied to the relevant manager or team and the details for the booking / event recodrd is updated accordingly.