Adding a SharePoint Calendar to Outlook
1. Click on the calendar you want to add on the Sharepoint site. Make sure you are in Classic View, so you can see the toolbar in SharePoint. (if you're not in Classic View, you should see a link to it in the lower right hand corner of the page - click on Switch to Classic View.
2. Once you see the toolbar at the top of the page, click on Calendar, then go towards the middle of the toolbar and click on Connect to Outlook:
3. You should then get a popup window, click Open:
4. Then you will get another popup, click yes:
5. You should now see the calendar listed in your Outlook calendars list.