Firstly, log in to either Outlook Online or within the app.
Then you want to the calendar icon located at the bottom left hand corner.
Then you want to go to 'Add Calendar' which is below the mini calendar you can see.
To add another calendar, this can either be a person or a school calendar.
You want to go to 'Add from directory' then type in the person or schools email address. The email address will then populate, you then want to click on the email address and then select 'Add'.
When you have pressed 'Add' the person or schools calendar will appear in your Outlook Calendar.
If you want to switch off the calendar. You can simply do this by pressing on the calendar you switch off. The tick that is within the circle should turn to just white.