Head to the stranded ship marked in the map. It will be easier if you have liberated Welshore Wrecker's House outpost. Once you're near the area, you have to avoid detection from the enemy patrols so you have to employ stealth. Get the Recurve Bow and if available, the GP9 as well since it has a Suppressor attachment. Move carefully and slowly. Try to move behind covers and foliages. Most importantly, use your camera to tag targets and monitor thier movements. Take note that the guards MUST NOT be alerted. That means they must not find the body of their comrades, create explosions, miss your shots, kill their allies while they're nearby, etc. The most efficient way would be luring them away from their buddies by distracting them with thrown rocks.
You have to loot the intel from the body of the yellow-tagged enemies. After killing and looting all three of them, make your way to the control room and operate the radio there. After listening in, you have to engage the enemies and take them all out the conventional way. The mission will be complete after killing all enemies.