Accessing Webmail Calendar.
Login to your webmail, you should see 3 webmail client provided for you. For webmail base with calendar feautures, you need to use Horde®.
Once logged in to horde, Expand the Organizing menu, you will see calendar option there.
Here is how your webmail calendar looks.
Adding a New Event
Click on plus "+" icon the date you prefer and start creating new event. Click Save to when you filled it all.
Your event is now created!!!