Click the + icon in the lower right corner. The clock is a widget, the one made by HTC. This is the place to go for adding widgets, shortcuts, etc., to your screens.
It is for help but don't clutter it up with basic things that are in the manual. It pushes useful threads to the bottom and to the next page. If you are new to a device don't you think the smart thing would be to read the book that came with it.