There are LOTS of YT videos that walk you through the airport and flight experience.
But to summarize:
Pack a backpack for the plane with things you'll want to access during the flight - headphones, devices, chargers, medications, your wallet, small toiletry items, snacks, inflatable pillows, eye masks, etc. You won't put that in the overhead bin but keep it under your seat for easy access. The backpack can double as a headrest or footrest if need be.
Keep a separate neck wallet or other small pouch that can hang around your neck and go under your clothes and put your passport, ID and cash in there. Keep that handy while going through the airport where you'll need it for going through security. During the flight, you can tuck that into your backpack, and it's easy to grab it again when you're at the destination airport. (When you get to Europe, you'll find it useful when you're traveling on crowded trains and metros and want to keep your valuables close to your body and out of sight.)
So for the flight -first of all download your airline's app. You'll get your boarding pass, and all the information (like which gate) on there.
If you're checking a bag, go to your airline's counter and do that first.
Now follow the signs to the Security line (TSA) and be prepared to show your passport and boarding pass. Then for the screening, be sure to take everything out of your pockets. You may have to take off your shoes and/or take electronic devices out of your carryon luggage - it varies but they will tell you.
After the screening, follow the signs to your concourse/gate. There will be a departure board showing which gate your flight is at if you want to double check.
When you arrive at the gate, hopefully you'll have a little down time and now you can maybe go get a drink, snack, gum, magazine, etc at one of the airport shops. It will be a long flight so go ahead and treat yourself!
On your boarding pass it will tell you which boarding zone you are in - For example: Zone 4. When it's time to begin boarding the gate agents will make announcements for each zone, so WAIT UNTIL YOUR ZONE IS CALLED before getting in line. A rookie mistake is to start lining up for boarding when your zone hasn't been called yet.
You'll scan your boarding pass from your phone - or a printed pass if you have one - and then get on the plane, find your seat, and quickly stow your bag in the overhead compartment above your row (hopefully!). Listen to the announcements on board because they will tell you which way to put it in for that particular aircraft. Take your seat, buckle in, and get settled.
You will need to stay seated when the seat belt sign is on. When the sign goes off, you can get up to use the lavatory, but stay buckled in otherwise. There is a call button for the flight attendant at your seat, but only use that if you're sick or need assistance - it's not just to order drinks!
The meal is usually served within half an hour of take-off when headed to Europe. Then they will dim the lights so you can relax and maybe get some sleep. You can read, watch movies on the IFE, listen to music - it can be a pleasant time to just unwind and anticipate the trip.
Have a great time on your study abroad, and HAPPY BIRTHDAY!