Navigate to https://outlook.office.com/calendar/

This will bring up a dialog box where you can enter in an email to share your calendar with. Click the "Enter an email address or contact name" field and enter the recipients email address here.

This will bring up a dialog box where you can enter in an email to share your calendar with. Click the "Enter an email address or contact name" field and enter the receipents email address here.

Click the "Enter an email address or contact name" field.

This field uses the same information as your Outlook "To:" field. So it may populate the email address for you. 

Note:
This field uses the same information as your Outlook's "To:" field, so it may populate automatically after a few characters are entered.

Next, select what access you would like for this person to have to your email.
Can view when I'm busy - They can only see when you are available or busy. No other details are available.
Can view event titles and locations - The titles of all meetings and locations, (if available) can be viewed, other attendees are not available
Can view all details - Can view everything about the meeting.