Task: Our friends group has arranged a get-together for the upcoming Monday, so I'd want to add an event on the calendar app and label it "Get together." 
Steps:
open the Calendar app
click on the add button at the bottom right corner of the screen
select event option
enter title name Get-Together
click on the date
select 25 september
click on the ok button
click on the save button at the top right corner of the screen