Are you clicking on the image or have you opened the Disk Utility application?
To find the application you need to find it.
To do that click on the blue Finder face in the dock.
Then a window like this will appear.
It will look similar to the above. Now you want to tell it how to show you what is inside.
Select the Column view, it makes it easy to find things.
Now you can navigate to the Applications folder, inside of that is Utilities folder, inside of that is Disk Utility.
That is one way to get to it.
Better yet is to use Spotlight, that is the magnifying glass looking thing in the top right corner of your screen or in the top right corner of the Finder window.
Like it shows above. Double click that item and it will open.
Now you can select your hard drive (top or second one down).
When you do it will work like it should.