Usually check-in begins 2–4 hours before scheduled departure and closes
40-60 minutes before departure. However, at some airports international
flight check-in may require additional safety control procedures and the
check-in may take more time. Keep this in mind when planning your
arrival to the airport. The flight ticket always displays the local
departure and arrival time.
A passenger late for check-in is denied the boarding.
After passenger's check-in, the airline staff member check in your baggage and give you the boarding pass with the number of your seat and baggage tag.
Then you should listen to the announcement (or look at the airport timetable) about boarding. You should then go to the gate indicated in your boarding pass or in airport timetable.