Please note that most of this stuff should already be covered in the "help" menu. But in case you MUST HAVE a web page to look at, here's one for you :-)
You cannot do anything useful by clicking on the central map window, except to give it focus for your arrow keys to move you.
Generally speaking, you can drop things from the top window, or pick up things from the bottom window, with the right button. If you have a three-button mouse, this is the #3 button. If you have a ONE-button mouse, this would be shift-click.
To apply an object (use, wear, ...), click with your middle button. Or if you don't have a middle button, control-click. [Think "control the object"]
To just examine something in either window, left-click.
"Hi therewill make your character say 'Hi there' to anyone around. Note that you are not supposed to put on a closing ".