In the calendar you get two options, you can either use the 'Default Calendar' or if you want to add your own calendar click '+Add Calendar'
Menu >> Settings >> School >> Calendars
Menu >> School >> Calendars
If you like to add a calendar click '+Add Calendar' and a popup calendar setup page will appear.
Title > Start and End date (from, to) > Weekdays selection > Select event visible to > Submit
To Add a New Event / Holiday click on the required date. An 'Add New' pop-up will appear. Here you select Event and Holidays from the options that are shown below.
At the Event Tab -
Calendar >> Click on date to add event >> Add event and details >> Submit
Similarly with the 'Holiday' section
Calendar >> Click on a date to add holiday >> Select holiday section >> Add a holiday and details >> Submit