As long as you’re tracking this quest with your Pip-Boy, the map should show you the location of this objective. Fast travel there if possible, but otherwise head somewhere closer and then just walk. When you arrive you will get an updated objective.
Tune your Pip-Boy’s radio into Courser Signal. This will display an on-screen signal strength, and your goal is to get that up as high as you possibly can. This will take you to the Greenetech Genetics building, and you should be ignoring all others. For example, we went into the C.I.T. Rotunda as we followed the signal, which was incorrect. Just head for Greenetech Genetics and make your way inside.
You can stop your radio from tracking the signal, something we forgot to do. You don’t have to, but the noise that tells you you’re getting closer is quite annoying. Plus, you are on a linear path now, so there is no way you won’t find the Courser just by ascending to the top of the building. Go inside and let’s get started.
We’re not going to hold your hand through the entire journey to the Courser, since that is basically the same as telling you how to kill every single enemy in the game. It’s really not that hard, just be patient and try to engage your targets before they engage you. Be on the lookout for turrets and traps, and make sure you have a good companion along for the ride. We opted to go with Cait, since she uses a shotgun and there is quite a lot of close quarters fighting in this section.
Continue to fight your way to the top of the building, ensuring that you loot all bodies and rooms before you move on to the next. You will find lots of weapons and ammunition, as well as aid that can help replace what you will inevitably use during the quest. You’ll also want to be on the lookout for a Missile Launcher and several Missiles, a clear indication that you’re in for a big fight.
Killing the Courser is tough if you don’t have the right formula, which is why you’ll be happy to know that we have the right formula. If you are stuck, travel somewhere and snag as many Cryogenic Grenades as you can. These will freeze your target, allowing you to use Missiles (or whatever big exploding things you have) without taking damage in return. We used about five of these grenades, and by the time we were done the Courser was defeated. You can also try the Cryogenic Mines if you have them, but stay away from things like Molotovs and Fragmentation Grenades. They didn’t seem particularly effective. Oh, and be sure to utilize V.A.T.S. if you get yourself into a spot.
This is done by simply looting the body of the Courser itself, and you’ll have to do it if you hope to complete the quest. You can continue searching the area if you’d like, and if you see a Synth called K1-98, speak to her to find out how you can set her free. There is no immediate harm in doing so, and you never know how that will change things down the road.
If you’d like to continue with the main quests, head to Fallout 4: The Molecular Level, or you can visit USgamer’s Fallout 4 Walkthrough and Guide.