This aims to be a bit more in-depth to start as a introduction to Ghost Recon Wildlands as well as a guide to completing the achievement
Video playthrough is at the end of the description
Once you start, you'll be outside the safehouse in the western edge of Itacua Province. There will be a yellow area marked to the east (ignore other yellow markers if present as these will be for dlc missions).
Quick note to say here that if you have a Ubisoft account, you can grab additional weapons (G36C assault riftle, PSG1 sniper, FAL, Sig556 Llama, SASG). Shotguns are not great in this game so the SASG can be ignored and the FAL is not a great weapon but the Sig556 or the G36C are both good assault rifles, and having a sniper rifle is a good idea - the PSG1 fires fast for a sniper though it's a little underpowered.
Grab a vehicle (or call in one from your rebel support menu) and use the GPS and drive towards the arrow. It's better to stay to the roads for now as the ground is more than a little uneven and vehicle handling is pretty poor - helicopters will be your usual choice for moving around unless surface to air missile sites are nearby
After you follow the GPS, you'll come to the end of the road with around 250m or so left to your target. There will be a stair case in front of you with a enemy visible at the top. As soon as you climb the first flight, you will get a prompt to use your recon drone or binoculars.
Take down the first enemy from a distance and proceed. You'll get a menu tutorial for sync shot and up past the next flight of stairs will be two enemies, one sitting and one walking back and forth. Use the sync shot on the one moving and line up on the one sitting. Your AI partner will shoot his target as soon as you open fire.
Carry on towards the top of the mountain. On your map as you proceed will be green icons that indicate supplies needed to progress your rebel support options. Make sure to grab these as you also get XP for tagging each supply.
The next target will be moving back and forth along the path - wait for them to approach or head up along the northern side of the buildings in order to take them down away from the lieutenant that is your target.
Note that there is one more sicario in the watchout hut at the end and move in on your target. If you get close enough to the target, you will get the option to grab them. Wait until they begin to move away from you again and move up - crouch walking will not alert them - and grab when close.
Take a moment to learn the movements as the target may attempt to flee if they see you approaching. before you move in.
Once you have them, you can knock them out, release them or interrogate them, the options will come up onscreen. Interrogate them to find the location of Amaru then knock them out.
At this point, take a moment and go to where the lookout was. You'll be overlooking an area that has four more sicario's in. Either using sniper shots/sync shot or by sneaking down the stairs and getting closer, take all of them out to collect a couple more supplies and also your first legend pickup in an armchair near the tower. This will give you the Your First Legend
achievement and a step closer to the various achievements related to legend collection
You will be around 2km from Amaru so grab a vehicle and drive that way. Vehicles are pretty study so can be driven down the side of a mountain but can get caught on rocky outcrops. Watch out as well for a river around 500m from the target. Most likely you will arrive at the western edge of a farm. There is a small hill to the west which will give a good line of sight so crouch/lie down at the top and recon the area. If you watch the movements, you will see moments when you can take shots at isolated targets. If you have picked up the supplies, you should have hit level 2 by the time you arrive. It's recommended to get the next step of sync shot at this point as this will help with taking down multiple enemies at once
If you don't have a sniper rifle you may have to get closer - for this mission if you do alert the enemies, they will react to you but won't call in reinforcements so if you need to 'go loud', there aren't any major repercussions.
Amaru is in a locked cell in the main building so as long as you don't throw a grenade in, he is pretty safe from any stray weapon fire.
Note as well that enemy vehicles can travel along the road to the north of the farm; if you are too close to the road, or otherwise alert them, they may join in the fight. The driving enemy could also be an informant - if you can capture then, they will reveal the location of a resource (skill points, unique weapons, or bonus medals) but this isn't needed to complete the mission.
Once all the sicario's are dead, make sure that you have collected all the supplies then interact with the door to break the lock (or shoot it if you prefer - use your handgun). Interact with Amaru to lead him (you can get him to stop if needed) and best way to leave is using the helicopter parked out front.
Get in the driver seat and wait for Amaru to join you. As with driving vehicles, AI team mates will automatically teleport into the vehicle if you leave them behind but target characters, and real life team mates you will need to wait for them to embark.
Once you fly back to the safe house indicated (Itacua Echo) and click on Extract on the door, a cut scene will play out.
After the cut scene is complete, the mission will be complete and the achievement should pop.
You should also hit level 3 at this point. Note as well that the M40A5 is in a box immediately in front of the safe house (if you don;t have a Club account or don't like the PSG1) - the M40A5 is a workhorse sniper and will serve you well for a good portion of the game).
It's also your first step on the Sniper Rifle Fanatic achievement