To find out your flight’s terminal, you generally just need to check your airline confirmation or flight itinerary. This can be found either in your email confirmation, or on the airline’s website closer to the day of departure.
The flight terminal is sometimes included on your boarding pass, along with the gate number, when you check in. Additionally, a Google search of your airline and flight number typically returns the terminal along with the flight details.
Sometimes the best way to determine your terminal is simply confirming which terminal your airline operates out of. Some airports assign airlines to specific terminals. You can check this by visiting the airport’s website, though be sure to check for your specific flight, as some airlines operate out of multiple terminals.
Monitors and signs within the airport will also be able to direct you to the correct terminal.
Even if your flight confirmation lists a terminal, be sure to check again closer to departure, as airlines sometimes switch both gates and terminals.