welcome to LQ.
Originally Posted by boxcar99
I'm very new to Linux. What is a desktop enviornment?
In this context it is the graphical interface that you interact with. There are many different ones that come with linux mint. If you go http://linuxmint.com
you should be able to see there is "Cinnamon", "MATE" and "KDE". Each of these will have a slightly different way of changing things like the mouse pointer. Do you know which one you are using?
Note that generally you should not be manually downloading software or themes etc using your web browser. Instead you should use the configuration tools and package manager ("Software center" or similar) provided by Mint.