Issues with my scroll pad...

I have an macbook pro OSX and yesterday my screen froze so I shut the it off and restarted it. Upon restart my scrolling to the bottom left corner of the screen(which shrinks all the windows you have open) was not working anymore. Can anyone advise if I can get this working again. It is a very handy tool and I miss it.

Click on the apple in the top left corner and go to system preferences then go to trackpad
then you can select bottom left or right your choice.

Thanks OSXX, I did that but it still doesn't work, but I did find a feature that I didn't know about before which does the same thing by using 4 fingers and swiping from top of pad down will also show all windows that are open.