You can see when there is still availability under the experience. There you can also book directly.
An overview of all experiences on a certain day can be found in the schedule
The availability is shown in different colors: red (full), yellow (almost full), green (available) or gray (on request). You can make a reservation for days that are 'on request'. The planners do their utmost to schedule you for that day.
Do you already have a voucher? Then go to reservation