After finishing the tutorial, you have to find a place to make a safe house. Once you clear it, explore and either find a vehicle, or a gas can for your original vehicle. I had a rucksack spawn inside my vehicle, if you don't, search containers and house until you do. Then transfer it from your inventory to the car boot by walking to the back of the vehicle and then transferring it. Drive the car to the parking spot marked with a large "P" outside your safe house. Exit the vehicle and walk to the back and open the trunk. You will see an option to transfer straight to the safe house. Do this (RT I believe), and the achievement will pop.