Zombies have returned in Call of Duty: Black Ops Cold War. The undead horde doesn’t know when to quit. It’s time to take a squad of allies down into the depths of the underground laboratory to shut the operation down. You can at least try to keep it locked down until the next squad of people needs to venture down. A good way to make sure you can defeat the horde is learning how to use the Pack-a-Punch machine to upgrade your weapons. Luckily, the Zombie mode’s story objectives show you where to go and how to unlock the power.

The big key to unlocking the Pack-a-Punch is following the purple neon arrows. You find the first one when you enter the map, and on the right side of the entrance, open up the first door for 500 points. Inside, there will be an arrow leading up a stairwell, showing you the direction you need to follow to unlock the machine.

There will be another barrier at the stairwell that costs 750 points to unlock.

When you’re up the stairs, turn around, and the next neon sign will be all the way on the other side of the room. It directs you to another barrier, and this one costs 1,000 points to unlock.

You need to run all the way across the open field to the other side, following the quest objective, and destroy another barrier for 1,250 points to enter the facility’s entrance. The entrance to the facility takes a few seconds to unlock.

After you’ve opened the entrance, proceed down and open the door on the right. It costs 1,250 points.

The next door, after that one, is worth 1,250 points.

This will bring you the main facility room that’s a large open area. Proceed to the other side of the room where the quest indicator is showing, and open up the power room’s final door. It costs 1,750 points. You can now activate the power and a new objective.

The next objective is to turn on the terminals on both sides of the room. These are clearly shown where in the room you need to go. Turning them both on brings a portal in the center room. Enter it, and prepare to adventure into a new reality. It’ll be the same map as before, but there’s a dark glow to it, and everything is blue and glows.

Now that you’re in the new dimension return to the power room and go up the stairs. The neon purple arrows on the wall are a good way to tell if you’re going the correct way.

Once you’re up the stairs, you’ll be back at the open field of the map. Your goal is to make it to the Aether Tunnel and to reach it. You’re basically backtracking your way through the map where you previously came from. When you arrive at the quest objective, you’ll be able to go through it for 500 points. When you arrive at the end of the tunnel, look on the ground for the Pack-a-Punch machine part. It will be behind you.

Once you have it, return to the main power room. It’s a lot of going through the same areas you previously were, and if you ever find yourself lost, use the power neon signs to learn where to go. When you return to the main room, there will be a transparent Pack-a-Punch you can interact with, and when you do, you’ll return to the main reality, and you can now use the machine with your squadmates.