There are a few ways to do it, but here's what I do...

Under "detailed statistics," click on "departures."
Select whatever stats you want; I usually just choose "Scheduled departure time."
Choose an airline and origin city.
Choose a date, or multiple dates.
Submit!

Depending on the parameters of your search, you may end up with only a few flights or a few hundred. If needed, use ctrl+F (or the Mac equivalent) to search for your destination airport code to narrow down the results. You can then use the scheduled departure time, or whatever statistic(s) you selected, to confirm that you've found the right flight.

Hope that helps!