Click on the event you created, and click the Pencil icon to edit.
Click on the Find a Time tab to find a time you and your guests are free. A grey box will appear, and it can be used to highlight blank spaces in all guests’ calendars.
An alternative option: Click the Suggested times button located under the Guests tab located on the right side of the Calendar window. It auto-generates times for you quickly.
After you pick a time, click the blue Save button to send out google calendar invites.