How do I set how far in advance my clients can book on my website?

To set your advanced availability:

Go to Menu >> Booking System >> Booking locations
Click on the location you wish to set advanced availability for
Click on Advanced settings
Select Advanced bookings and set by choosing a time period
This controls how far in advance clients can request bookings e.g up to 3 months
Click back to save

Note - You will need to set this up on a per location basis to apply to any/all of your locations