1) Sign in to Outlook on the web.

2) In the bottom left-hand corner of the window, click the Calendar tab.

3) On the left-hand side, right-click the calendar that you wish to share. Then, click Sharing and permissions.

4) Choose the permissions level for the user who you wish to edit. You can also remove the user from your calendar permissions by clicking the "trash" icon. Once all desired permission changes are made, changes will be automatically saved.

Outcome

The permissions for the intended user are changed.