You'll get this achievement while playing through episode 5.
This is one of the achievements in the game which causes some people some trouble, when you get to the jungle you have to find the "Dharma van" from the TV show.
While playing through episode 5 you'll come to a point where you enter the jungle, when you get here you need to explore and look around for the van, to save you time looking around if you follow the video guide below you'll know where to go!
* Credit to elemen7s for the video