Check which terminal you will be flying from (this depends on airline and destination)
When you enter the terminal, look at the screens to see which desk/s you should check in at (also depends on airline and destination). Queue in front of a desk appropriate to your class of travel (Economy, Business etc). There will be a security check before you get to the desk.
When you get to the desk, put your suitcases on the weighing scales and hand the clerk your passports and tickets. You will probably be offered a choice of seats (window, aisle etc).
The boarding passes you will be given will show the numbers of the seats you have been allocated. Aircraft seats are numbered by rows (1, 2, 3 etc) starting from the front and by seat from left to right (direction of travel) so your seats may be 20A and 20B for example 20A being a window seat on the left of the aircraft. The boarding pass will also show which gate the flight leaves from.
Follow the signs through the security check, find your gate and browse the duty free shops while waiting for your flight.
When boarding starts, listen to the announcements as it may be done by seat rows.
When you arrive at your destination, after having passed through Immigration, follow everybody else to the baggage hall, check the screens for your flight number so that you know which carrousel to go to to pick up your suitcases. Do not take any food off the plane or the sniffer dogs will find it!
Have a good trip!