I'm also a noob at linux so to put it simple you need to go to the /etc folder and replace the yum.conf file.

I think for you it would be easier to log in as root and use the explorer.
Login with the username: root and your password.
Now use the explorer (found in the menu bar , called nautilus).
Navigate to the top level of your drive and find the folder called "etc". Here is a file called yum.conf. Replace it with the one you download. Just a simple copy/paste.