Log onto your SharePoint website and locate the calendar you wish to add to Outlook. You need to have permission to view or edit the SharePoint calendar before you can add it to your Outlook. There may be more than one calendar in the list. If you need to add several calendars, you can add them one at a time. See the image below.
Once you have selected the calendar you wish to add to Outlook, click "Calendar" under the "Calendar Tools" section located in the ribbon menu. Then click on "Connect to Outlook". See the yellow highlighted areas in the image below.
Click "OK" to accept Outlook as the application you want the calendar to open in.
Select "Yes" to add to Outlook.
If you experience any difficulty or need assistance with adding your SharePoint calendar to Outlook please submit a help request here: General TSS Help Request.