Usually check-in begins 2-4 hours before scheduled departure and closes 40-60 minutes before departure. However, certain countries and airlines may have additional security control procedures, which influences the check-in 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.