Click the Mailbox in the Folder List.

or

Click the Calendar icon in the Folder List or on the Calendar Nav Bar, then go to the date of the appointment, task, or note.

Click the appointment, task, or note to open it, then click Accept.

The appointment, task, or note is removed from the Item List in your Mailbox and appears in your Calendar only. The sender can tell you accepted the item by checking its status information.