On your calendar, you can indicate sets of time in which you are available and that you are unavailable for initial client calls.
Available times = times when clients can request a call with you
Busy/unavailable times = times that your calendar is blocked off so clients can not schedule a call; these override any available times.
Available and Blocked time slots can both be added by navigating to the Call Calendar tab and selecting the desired option from the "Add" button dropdown menu.
Step-by-step instructions on blocking off available time is here!
Learn more about adding recurring availability here.