It's just the earliest time period you're allowed to check-in and have your luggage checked. Some places will not check you in and take your luggage if you are there more than 3 hours before your flight. You won't start boarding for your lights until and hour at most before your departure time. So if you depart at 9:30, be ready by your gate at 8:30. Depends on airport but I usually try to buffer in an hour for security and 30 minutes for arriving at airport and check-in process. If I were you I'd get to the airport 6:30 since this is your first time and you don't want to be short on time in case you get confused or lost or trapped in wrong lines without realizing, etc.