It will be about 3 hours before your flight departs - so for a 7:20 flight, you'll probably be assigned a time in the 4:15 to 4:45 range. You will get a notice on your door the day before departure that will give you a time to get the ME bus. You'll need to be at the stop about 15 minutes before the departure time.
Your flight information will be on that notice. If anything is off, you're instructed to call to make corrections.