help with donated apple2 gs, please

[steve3 <xee@psnw.com>]

Hy,
someone donated an Apple IIgs to our school. Printer, monitor, everything. 
But we need a boot disk, I think. Anyway, when I turn it on, I get only a blue
screen, a ball rolling horizontally on a white line back and forth and the
message "check your start-up (something or other)".
    So, any ideas? Also, I have what appears to be a separate 3 1/4 floppy
drive, but no cable for it. WHere might I get a cable?
thanks for your help, steve w.