Start by creating a new calendar event.  Enter the title for the meeting and add the date and time.  Click the dropdown menu to add Zoom to your meeting.  You will now see the following image:  

Click on Authorize.  Click on your account, i.e.,

In the next pop-up window, you will see that Zoom needs you to allow access to some calendar events and email add-ons.  Scroll to the bottom and click Allow.

You should now be able to continue creating the calendar event as you would normally.