1) To add a custom event to your calendar, start by clicking the green + New Event button on the right side of the calendar.
2) Type in the description, start/end times and any notes. If you are an admin, you can assign this to whomever you like. Otherwise it will automatically assign to you.
3) After blocking this time, it will now appear on your calendar, as well as show on your admin's calendar so they know not to schedule you for that time.
4) Clicking on the event will slide over the details of it. This includes the start/end time, who's calendar it is on. You can also delete the event from here.