Kenny wrote:

On Win 7 PC when I press Home key from Desktop it opens Firefox, how do I do
this on a Win 8.1 laptop?

Install the software that came with the keyboard. You didn't identify
the maker and model of keyboard so you'll have to go look for the
install CD or check the maker's web site for the software they provide
for that keyboard. That is assuming their software also works under
Windows 8.

Why would anyone define the Home key to load any application? What if
you are viewing a web page and press Home to go to the top of the page?
Another instance of the web browser opens instead? What if you're in a
word editor and press Home to move the cursor to the start of the line?
Another web browser loads? Probably what you meant by "Home" is a
special-use key on the keyboard, like those used to load the web
browser, default e-mail app, increase/lower/mute audio, load Calculator,
and so on. The maker's software is used to map those special keys (they
send special scan codes) to functions or programs.