How to take screenshots in fluxbox.

First. Install gnome-screenshot (Or any other screenshot software)
sudo apt-get install gnome-screenshot
or
yum install gnome-screenshot

Or you might already have it installed.

Now...

1. cd .fluxbox
2. nano (Or whatever text editor you want.) keys
3. add to the bottom: None Print :ExecCommand gnome-screenshot

You can change print to whatever key you want. (Print = print scr on your keyboard.)

More info.