To suggest a time for a meeting, open a new email message and click on the icon to launch the Book A Time window.
The window will load your calendar and allow you to click and drag to indicate your available times. Give your meeting a title, and optionally specify a meeting length, location, and description. When a recipient ends up booking a meeting, all of these fields will populate onto the resulting calendar invite.
When you click Insert Times, the available time slots will be inserted into the email message you were composing.
When you send this message, your recipient will be able to the click the link that says "Click here to schedule a meeting". They will be brought to a landing page where they can select a specific time to meet. Only time slots that are still available (not busy) on your calendar will be displayed on the landing page.
When a recipient selects a time, they will receive a calendar invite for the meeting, and the meeting will automatically show up on your Google calendar.