The iPhone calendar is a convenient way to keep track of your upcoming appointments, parties and other scheduled events. If you have linked your Microsoft Exchange account with your device, Microsoft Outlook meeting requests, also called invitations, are easily responded to right from your calendar. Once you receive a meeting invitation, accepting the request takes just a few taps of your finger; accepted meetings are automatically put on your calendar.
Open the Calendar application on your iPhone.
Tap the downward arrow in the bottom right corner of the screen to reveal all pending meetings, then tap the invitation you want to respond to. Alternatively, go to your calendar and tap the invitation, which is outlined with a dotted line on the date and time of the suggested meeting.
Tap the "Accept" button at the bottom of the screen, under the full details of the meeting. The meeting will be put on your calendar sans the dotted line.