How to Invite People to Meetings in Outlook 2013
On the timeline at the top of the Attendee Availability page, click your preferred meeting time.
The time you pick appears in the Start Time box at the bottom of the Attendee Availability page. If you want, you can enter the meeting start and end time in the boxes at the bottom of the Attendee Availability page instead of clicking the timeline.
If you don’t see a time when everyone you’re inviting to your meeting is available, you can select a time that works for everyone from the list of available time slots in the Suggested Times window.