Use one of the many agencies that will pursue the airline for compensation on your behalf on a no-win, no-fee basis.

Note, however, that as we have no idea what the reason was for the delay we have no idea whether you are actually entitled to any compensation. Can you tell us the exact reason (we need more than "operational reasons" in order to figure out if your claim stands any chance) if this is known to you? And how late did you actually arrive at your destination?