With Schedulers, you can have a client schedule a date (or as many dates as you'd like) while booking you. You can have a user schedule a Shoot Date, or a Viewing Appointment right when they're booking.
To do this, you'll need to add your Scheduler to your Booking Proposal or Booking Page. To do this, go into your Booking Proposal or Page. Click the "Add Scheduler for the Shoot Date" button at the top of the page.
After the first scheduler for the shoot date has been added, you can choose "Add Additional Scheduler" to have your client pick a new custom date. This would be used for adding a new appointment when a client is booking.