You can drag contacts from Address Book or the Address Panel (Window > Address Panel) into BusyCal to attach contacts to events or To Dos.
Drag a contact into the calendar to create a new meeting with that contact. Or drag the contact onto an existing event to add them as an attendee.
Drag a contact into the To Do list to create a new To Do that is linked to that contact. The contact's name will appear in the Title field, and their phone number and email address will appear in the Location field, and a link to the contact will appear in the my URL field.
You can add a contact's info to an existing event by dragging the contact to the Notes field.
You can add a contact's address and phone number to an existing event by dragging the contact to the Location field.
You can add a link to a contact by dragging the contact to the my URL field.
Tip: In addition to contacts, you can drag files, Mail messages, Safari URLs, and other items to the my URL field to create links to those items.