how to enable 50Mhz Clock in DE2 board

If I understand right, you now discovered, that your design is working as expectable.

Your considerations about the impossibility of tracing design operation at 50 MHz by looking at a LED display sound plausible, if no external events are needed to advance the state machine.

Normally, people are feeding a 50 MHz clock to a design, because they want it to act fast. To visualize it's operation, you can use test tools like SignalTap - or a slow clock.