You MUST add at least 1 location to add a session to the calendar.
You can find the add locations page using the main menu:
SESSIONS > ADD LOCATIONS.
If you provide in-home services add a location named like:
In-Home or something similar.
If you conduct sessions remotely using meeting software you could create a location like:
Online Meeting or
location name is a required field. You don't have to save contact information for locations.