No matter how you've chosen to deal with the Skulls situation, you have to go north-east, towards a large mansion located near the east edge of the map. After getting close to it, stick to the paths on the left. You will have to do a little climbing and go past a guard with a searchlight. You can stop for a while after reaching the mansion and do a quick recon to mark the enemies.
Your current task is to get inside the mansion. Don't use the front door, but go the back instead by circling it from the left. There should be 2-3 guards here, but you can sneak up to them (hide behind the walls or crawl) and eliminate them (remember to Fulton them if you knock them out). Locate the back door shown in the picture above.
After entering the mansion, ignore the stairs on the right and go left. Follow the path marked by the candles. It will lead you to the basement. You can proceed through the rooms, because you won't encounter any enemies. In the last room, you will find Code Talker.