1) Tap the calendar icon at the bottom right of your screen:
2) Give the event a descriptive name. You can now add people to the event. Set the time and date. If people are free at the time of the event, a green user icon with a tick mark should appear; if people are unavailable, a red user icon with an X should appear. Add a location and fill in the other fields as applicable. When the event is set up correctly, tap the tick mark in the top right corner to save it: