This can be done from the beginning of the game, once you earn $43,125. Head to any of the Total Motors dealership and purchase the Merengue, under the standard vehicles section. Now drive 4km in it, the achievement / trophy will pop when you stop the vehicle or open Nudle maps.
Here is a guide with English commentary!
Here is a playlist of guides for this game!
https://www.youtube.com/playlist?list=PL-HeW6XkKdUKcpUn58waV...