Elex

Origin is a camp located East of the Domed City. Its an essential area for you and your companions and you'll spend a lot of time here levelling your charachter.

https://game-maps.com/ELEX/Elex-Abessa-Central-Map.asp

For the Achievement you need to complete a couple of quests:
Speak with Lloyd he will tell you to help the camp so go and speak with them.
Speak with Harleyhe will give you the quest, salvage work.
Defence of the Camp - EckhartYou need to send 3 of your companions, when speaking to them choose, 'go to origin'. then find Eckhart, tell him the name of the companions and you'll get experience, you only need to send 3 for the quest but keep going back to him after every companion to get more XP
Freeing the Camp Jonesy will ask you to kill some mutants, be sure that they dont kill any settlers. Jonesy himself can die and he is a trainer so keep him alive.

A foot in the doorAfter the above have been completed go speak with Loyd he will give you a key to the tower, this will be your new home, you can place map pieces you have collected on the wall and there is a chest for your excess inventory, this will also complete Promising living Arrangements
Finally
Salvage Work Harley requires a motor from a colossus. I recommend using ranged weapons, Daryls Revenge, the Staker, or upgraded crossbow are all effective. This is the most difficult quest of all the above, but as long as you take a companion, lots of health and a good ranged weapon its actually not hard.

once the last quest has been completed go back and talk with Lloyd and accept the achievement will unlock.

This area becomes a base for you and your companions and i recommend finding it as soon as possible. Speak with Anne and you can upgrade the camp, purchase a trader and A craft bench once you are mid-level, the trader has an infinite supply of Natural Elex so you can make as many potions as you can afford which will boost your stats.