Then download this version. I assumed that you had a 64-bit machine, because 32-bit computers are pretty obsolete. http://www.rarlab.com/rar/wrar510.exe
Install the program, and once you've finished, double click the file that you downloaded. It will open up the program, and show you a file sitting in it, like a folder would. Just drag that file to the desktop, and drag the file from the desktop into Horizon, then follow the essay above.
It's no problem. If you need any more help, post in the correct forum. Don't be afraid to hit the like this button on a few posts if they helped you.
I definitely look up to you iNfeCt, that was a clear, easy to follow tutorial and you helped this guy out perfectly. A job well done