The achievement is unlocked upon finding the fourth pod in the game. There are four pods that can be equipped. Pod 042 is 2B's pod at the start of the game. Pod 153 is assigned to 9S who uses it at the start of the game. Pods 042 and 153 are considered to be Type A pods. There are two other pods that can be discovered. They are referred to as Types B and C.
Pod type C can be discovered earlier than Pod type B. The earliest it can be discovered is when Jackass blows the demolitions opening up a path to the desert. Go through the path and turn left hugging the wall. Before long, you will get to an inlet with an oil pond and a save point. This is the oil field. From here, turn towards the desert center. The pod is not far from the opening to the oil field. It is a dark object lying on the sand. Although it does not have the telltale golden indicator, it can be picked up. This initiates a dialog with your pod. If you are playing as 2B when you discover it, the dialog will be with pod 042. If you are playing as 9S when you discover it, the dialog will be with pod 153. After the dialog, the pod will be equipped and can be configured if desired.
Note: If you are having trouble finding pod type C, it is easier once you have found the save points at both the oil field and the desert center. When these two save point icons both appear on your map, start from the oil field. Pull up your map and put a marker on the desert center. Now walk directly towards the marker looking for a dark object as you proceed. It is very close to the oil field so, if you have gone a third of the way to the desert center, you have gone too far.
Assuming that pod type C has been discovered, the earliest pod type B can be discovered is after the terrain change with a crater that uncovers a sewer entrance. If you follow this sewer, it will lead you to a save point near the Flooded City. Continue on a linear path. You will come to a large stone bridge. There are some enemies that you have to dispose of and, possibly, some gold enemies that are part of a mini-event.
Once you can freely control your character, you can fish off the bridge (use the left side with respect to your direction of travel from the save point). Look out over the water to a tall building. Cast your line between the bridge and the tall building to fish. I have gotten the pod when casting both close to the bridge and far from it. There is a good variety of fish here. You might catch a few before you find the pod. The pod is not that uncommon so it should not take long. If you have difficulty, vary your position on the bridge and vary your casting point.
As in the desert, when you discover the pod, a dialog will start with your character's pod. If you are controlling 2B, the dialog will be with pod 042, If you are controlling 9S, the dialog will be with pod 153. If this is the second pod you discover, the achievement will unlock.
Note: You may choose not to take the time to look for one or both pods in your first playthrough. If so, you can get them in another playthrough. Additionally, this achievement can be purchased at the secret shop that becomes available after the third playthrough. This achievement costs 50,000 gold if purchased.