If you receive an email message informing you of a meeting, you can open the email message then confirm whether you will be attending the meeting. The meeting in all of the guests' calendars will be updated to show your response.
To respond to a meeting request:
Click on the meeting invitation in your Inbox to open it
If you just want to accept or reject the invitation without adding a note or additional guests, click on the Yes, Maybe or No button under the meeting summary in the top section of the message
If you wish to add a note or additional guests, scroll down the email message and click on the More Options link in the second section of the invitation
You calendar will open and the event will display.
Click on the drop-down arrow to the right of the Yes, No and Maybe buttons
Choose to Add a note
Add a note and change your RSVP status if required
Click on Done
Click on Save to save the updated meeting in your calendar
To propose a new time for a meeting:
Click on the meeting in your calendar
Click on the drop-down arrow to the right of the Yes, No and Maybe options
Choose Propose a new time
Choose your proposed start and end date and time
Add an optional message to the meeting organiser
Click on Send Proposal