Here i will show you how to do that
As you progress ingame, you’ll get the mission for x-16 by the Bartender at the 100 rads bar. After you complete it, you’ll be able to talk with General Voronin (Duty Leader), he can be found at the duty Barracks. Now that you are able to talk with him, you can offer him your assistance. Voronin will give you 1 Special Mission and several basic Sidequests for example: Killing a Stalker or clearing an area of Mutants. After you have done several Missions for him, you should be able to join Duty. Joining will grant you Duty Armor and their respective Weapons. Note that you will be permanently hostile with Freedom, meaning that they’ll shoot you on sight.
Alternatively, you can help the Duty squad which camps just east of the Freedom base, helping them gives a massive boost to your reputation with Duty.
Good hunting Stalkers!
I hope that this Guide was Useful for you
If you have any questions, feel free to ask me in the comments below!