Timer/Strobe

I am new to programming microcontrollers, but I almost have my project done. The only thing left to do is to output a strobe that will oscillate between high and low. The duty cycle would ideally be shorter than the system clock, but doesn’t have to be. If anyone could let me know how to output a strobe based on the clock, or let me know how to just output the clock that would be great.

Thanks,

Eric