This The Last of Us 2 Walkthrough for Chapter 6: Seattle Day 1 – The Stadium has you get to know your base and has locations for all collectibles including 4 Coins.
Follow Manny. Once you reach the cafeteria, a few dialogues will pop up for more story moments. Get into the lunch line and Manny will meet up with you. Continue following Manny, through the doors and up the stairs. When you enter your room there are a few items you can interact with but more importantly, you need to go to your bottom bunk and interact with your backpack.
Coin – Alaska
As soon as you grab your pack in your room, follow Manny and Mel outside, and turn left towards two WLF members talking on a balcony, and a coin will be on the ground near them.
Coin – Maine
As you move down the stairs towards the center of the stadium, you’ll take a right and move through an area where people are washing and drying laundry. When Manny and Mel turn left to go down the last few sets of stairs to the kennels, move past the stairs to a row of wooden benches full of laundry, and you’ll find a coin on a bench.
Play with the dogs for a bit by throwing the ball (the same way you throw any item). Exit the little kennel to continue.
Coin – New Jersey
As you enter the tunnel, look to the right (where the WLF mural is) and pick up the coin under it.
Sharp Shooter Trophy
Check out some guns and go to the shooting range, get some good shots in and beat Manny to unlock the Sharp Shooter Trophy.
Coin – Vermont
After you try out the shooting range, exit into the hall where Mel and the dog are waiting, but go left past a workbench, and look into a steel cabinet full of ammo to find the coin stashed at the edge.
Head forward and hop into the back of the truck. Your conversation with Mel will be interrupted by Seraphites. Shoot them until your drive comes to an end. When it’s over, enter the warehouse and close the door behind you to begin the next section: Seattle Day 1 – On Foot.
Source: IGN.com The Last of Us 2 Walkthrough Chapter 6: Seattle Day 1 – The Stadium