1. Link a new calendar to connect your Google calendar.
  2. Enter the email address associated with your Google calendar and click Sign in With Google:

3. Click Allow on this consent screen:

Why is FreeBusy requesting these permissions?

FreeBusy automates meeting scheduling for you by reading availability from your calendars so it knows when it’s possible for others to propose meetings with you, and by auto-creating events in your calendars when people propose meetings with you. In order for FreeBusy to correctly calculate your availability it needs to show you all the calendars in your Google account so you can choose which ones are yours and which are just shared with you.

FreeBusy does NOT delete, download or export your calendar data. “Delete” is mentioned in the above consent screen only because FreeBusy needs the ability to reschedule and cancel meetings scheduled via FreeBusy booking pages.