1. Log into outlook web app via https://exchange.infoquest.com/ > In the top right click Calendar. Right Click the shared calendar and click Share Calendar. Enter the email address of the person(s) you want to share it to and click Send. This sends an email to the user in question to accept the shared calendar invitation.
THIS IS THE IMPORTANT PART
2. The user now needs to open this email on their iOS device. Within the invitation email there is a link at the bottom under “To subscribe to this calendar using an Internet calendar-compatible program, such as Microsoft Outlook 2007 or a later version, copy and paste the following Web address into your Web browser:”
3. Tap the link on the iOS device ending in .ics and you will receive a notification on the phone asking if they want to "Subscribe to the calendar "shared calendar name"?" Tap Subscribe and now you will see the shared calendar under the Calendar app on the iOS device.
Open 'Settings' on your iPhone or iPad and tap on 'Mail, Contacts, Calendars'. ...
Scroll to 'Accounts' and look for 'Subscribed Calendars' and tap on it. ...
If you have more than one subscribed calendar, then select the one you want to remove and then, tap on 'Delete Account'.