If you're having difficulty with placing the files on the root directory of your site, then you're likely to run into other issues as you proceed to the next steps. I found the
tutorial on installation here very easy to follow and managed to place the forum on my site within about 20 minutes, but it does require that you have at least a rudimentary knowledge of things such as FTP and working with cPanel, MySQL and several other things on the server side. I found this video tutorial on YouTube which demonstrates the process quite well, but my best advice is to take your time. Double check each operation before you click save, as backtracking mistakes is quite difficult in things such as this.
Need any specific guidance, feel free to send me a PM and I will try to assist you