Help For a program, 1kHz -10kHz squaregenerator, f screened on lcd


i have to write a program for my mbed lpc1768. A square wave generator with a volume of 1kHz-10kHz is to be generated and the frequency is to be displayed on an lcd. Since I have no idea and am also currently doing a time-consuming internship, it is very difficult for me to realize this.
I would appreciate help.