congratulations on choosing slackware, and fluxbox too (my personal favorite)!
for fluxbox themes, you've got two folders usually inside the compressed theme file you downloaded. there's a "styles" folder and a "backgrounds" folder. just copy these folders over to "/home/user/.fluxbox/" where "user" is the name of the user obviously. just in case you're not entirely sure how to do this, i'll show you. let's assume you've downloaded a file named "theme.tar.gz" into your "/home/user" directory:
Code:
cd
tar -xvvzf theme.tar.gz
mv backgrounds /home/user/.fluxbox/
mv styles /home/user/.fluxbox/
again, where "user" is the name of the user. this should be all you've gotta do. then check "Fluxbox-menu"->"Styles" and it should be there. you may need to restart fluxbox though, but usually you won't.
unfortunately, you can't have icons on the desktop in fluxbox. but you can make links to directories and files in the fluxbox menu. just use your favorite editor to edit "/home/user/.fluxbox/menu". when you see that file, you shoul understand how to do it, it's sort of self-explanatory. if you've got any more questions, feel free to ask, and welcome to LQ.