If you have access to view another person's calendar but you are not able to make changes to appointments despite being authorised to, you can fix this by:
- Asking the owner of the calendar to go to Calendar Permissions when in Outlook;
- Selecting your name from the list, or adding your name by clicking Add and selecting you from the list;
- Click on Permission Level and select "Editor" or
- Make sure the "Edit All" button is ticked against your name, to make sure your permission level is high enough to be able to make changes.
- Click Apply/OK
This should then allow you to edit appointments as required.