icon on lower left hand corner of display screen when turning off the computer

Re: turning the computer off.

The icon on the bottom left of the desk top.

I used to be able to use my left click mouse.

I got additional information when I used that left mouse.

Now, it seems that I have to use the right clicker on the mouse to turn off the computer and get less information.

How do I change it back to the original use of that icon.